<PAGE>
                               EXHIBIT 10.30

                         REGISTRATION RIGHTS AGREEMENT

     REGISTRATION RIGHTS AGREEMENT, dated as of November    , 1997 (this 
"Agreement"), by and between Prime Group Realty Trust, a Maryland real estate 
investment trust (the "Company"), and Security Capital Preferred Growth 
Incorporated, a Maryland corporation (the "Investor").

     WHEREAS, pursuant to that certain Series A Preferred Securities Purchase 
Agreement, dated as of November 11, 1997 (the "Purchase Agreement"), by and 
among the Company, Prime Group Realty, L.P., a Delaware limited partnership, 
and the Investor, the Investor has agreed to acquire 2 million shares of 
Series A Cumulative Convertible Preferred Shares of Beneficial Interest, par 
value $.01 per share, of the Company (the "Preferred Shares"), all of which 
may be converted into the Company's common shares of beneficial interest, par 
value S.01 per share (the "Common Shares"), pursuant to the terms of the 
Preferred Shares; and

     WHEREAS, in connection with the Purchase Agreement, the Company has 
agreed to register for sale by the Investor and certain transferees, the 
Preferred Shares and Common Shares received by the Investor upon conversion 
of Preferred Shares (collectively, the "Registrable Shares"); and

     WHEREAS, the parties hereto desire to enter into this Agreement to 
evidence the foregoing agreement of the Company and the mutual covenants of 
the parties relating thereto.

     NOW, THEREFORE, in consideration of the foregoing and the covenants of 
the parties set forth herein and for other good and valuable consideration, 
the receipt and sufficiency of which are hereby acknowledged, subject to the 
terms and conditions set forth herein, the parties hereby agree as follows:

     Section (i)    Certain Definitions.  In this Agreement the following 
terms shall have the following respective meanings:

     "Accredited Investor" shall have the meaning set forth in Rule 501 of 
the General Rules and Regulations promulgated under the Securities Act.

     "Affiliate" shall mean, when used with respect to a specified Person, 
another Person that directly, or indirectly through one or more 
intermediaries, controls or is controlled by or is under common control with 
the Person specified.

     "Commission" shall mean the Securities and Exchange Commission or any 
other federal agency at the time administering the Securities Act.

     "Exchange Act" shall mean the Securities Exchange Act of 1934, as 
amended, and the rules and regulations of the Commission thereunder, all as 
the same shall be in effect at the 

<PAGE>



relevant time.

     "Holders" shall mean (i) the Investor and (ii) each Person holding 
Registrable Shares (which term, for purposes of this definition shall include 
Common Shares that may be issued upon conversion of outstanding Preferred 
Shares) as a result of a transfer or assignment to that Person of Registrable 
Shares other than pursuant to an effective registration statement or Rule 144 
under the Securities Act.

     "Indemnified Party" shall have the meaning ascribed to it in Section 
6(c) of this Agreement.

     "Indemnifying Party" shall have the meaning ascribed to it in Section 
6(c) of this Agreement.

     "Person" shall mean an individual, corporation, partnership, estate, 
trust, association, private foundation, joint stock company or other entity.

     "Piggyback Notice" shall have the meaning ascribed to it in Section 3(a) 
of this Agreement.

     "Piggyback Registration" shall have the meaning ascribed to it in 
Section 3(a) of this Agreement.

     "Preferred Shares" shall have the meaning ascribed to it in the recitals 
to this Agreement.

     The terms "Register," "Registered" and "Registration" refer to a 
registration effected by preparing and filing a registration statement in 
compliance with the Securities Act providing for the sale by the Holders of 
Registrable Shares in accordance with the method or methods of distribution 
designated by the Holders, and the declaration or ordering of the 
effectiveness of such registration statement by the Commission.

     "Registrable Shares" shall have the meaning ascribed to it in the 
recitals to this Agreement, except that as to any particular Registrable 
Shares, once issued such securities shall cease to be Registrable Shares when 
(a) a registration statement with respect to the sale of such securities 
(other than the Company's registration statement on Form S-11 (File No. 
333-33547)) shall have become effective under the Securities Act and such 
securities shall have been disposed of in accordance with such registration 
statement, or (b) such securities shall have been sold in accordance with 
Rule 144 (or any successor provision) under the Securities Act.

     "Registration Expenses" shall mean all out-of-pocket expenses (excluding 
Selling Expenses) incurred by the Company in complying with Sections 2, 3 and 
4 hereof, including, without limitation, the following: (a) all registration, 
filing and listing fees; (b) fees and expenses 


                                        2

<PAGE>

of compliance with federal and state securities or real estate syndication 
laws (including, without limitation, reasonable fees and disbursements of 
counsel in connection with state securities and real estate syndication 
qualifications of the Registrable Shares under the laws of such jurisdictions 
as the Holders may reasonably designate); (c) printing (including, without 
limitation, expenses of printing or engraving certificates for the 
Registrable Shares in a form eligible for deposit with The Depository Trust 
Company and otherwise meeting the requirements of any securities exchange on 
which they are listed and of printing registration statements and 
prospectuses), messenger, telephone, shipping and delivery expenses; (d) fees 
and disbursements of counsel for the Company; (e) fees and disbursements of 
all independent public accountants of the Company (including without 
limitation the expenses of any annual or special audit and "cold comfort" 
letters required by the managing underwriter); (f) Securities Act liability 
insurance if the Company so desires; (g) fees and expenses of other Persons 
reasonably necessary in connection with the registration, including any 
experts, retained by the Company; (h) fees and expenses incurred in 
connection with the listing of the Registrable Shares on each securities 
exchange on which securities of the same class or series are then listed; and 
(i) fees and expenses associated with any filing with the National 
Association of Securities Dealers, Inc. required to be made in connection 
with the registration statement.

     "Registration Request" shall have the meaning ascribed to it in Section 
2(a) of this Agreement.

     "Rule 144" shall mean Rule 144 promulgated by the Commission under the 
Securities Act. 

     "Securities Act" shall mean the Securities Act of 1933, as amended, and 
the rules and regulations of the Commission thereunder, all as the same shall 
be in effect at the relevant time.

     "Selling Expenses" shall mean all underwriting discounts, selling 
commissions and stock transfer taxes applicable to any sale of Registrable 
Shares.

     Section (ii)   Demand Registration.

     (a)  Upon receipt of a written request (a "Registration Request") 
delivered not earlier than 120 days prior to the first anniversary of this 
Agreement from Holders holding at least 50% of the aggregate of the number of 
Preferred Shares then outstanding, the Company shall (i) promptly give notice 
of the Registration Request to all non-requesting Holders and (ii) prepare 
and file with the Commission, within 45 days after its receipt of such 
Registration Request a registration statement for the purpose of effecting a 
Registration of the sale of all Registrable Shares by the requesting Holders 
and any other Holder who requests to have his Registrable Shares included in 
such registration statement within IO days after receipt of notice by such 
Holder of the Registration Request.  The Company shall use its reasonable 
best efforts to effect such Registration as soon as practicable but not later 
than 120 days after its receipt of such Registration Request (including, 
without limitation, the execution of an undertaking to file post-effective 
amendments and appropriate qualification under applicable state securities 
and real estate 


                                        3

<PAGE>

syndication laws); and shall keep such Registration continuously effective 
until the earlier of (i) the third anniversary of the date hereof, (h) the 
date on which all Registrable Shares have been sold pursuant to such 
registration statement or Rule 144, and (iii) the date on which, in the 
reasonable opinion of counsel to the Holders, all of the Registrable Shares 
may be sold in accordance with Rule 144(k); provided, however, that the 
Company shall not be obligated to take any action to effect any such 
Registration, qualification or compliance pursuant to this Section 2 in any 
particular jurisdiction in which the Company would be required to execute a 
general consent to service of process in effecting such Registration, 
qualification or compliance unless the Company is already subject to service 
in such jurisdiction.

     Notwithstanding the foregoing, the Company shall have the right (the 
"Suspension Right") to defer such filing (or suspend sales under any filed 
registration statement or defer the updating of any filed registration 
statement and suspend sales thereunder) for a period of not more than 90 days 
during any one-year period ending on December 31, if the Company shall 
furnish to the Holders a certificate signed by an executive officer or any 
trustee of the Company stating that, in the good faith judgment of the 
Company, it would be detrimental to the Company and its shareholders to file 
such registration statement or amendment thereto at such time (or continue 
sales under a filed registration statement) and therefore the Company has 
elected to defer the filing of such registration statement (or suspend sales 
under a filed registration statement).

     (b)  The Company shall not be required to effect more than one (1) 
Registration pursuant to this Section 2.

     Section (i)    Piggyback Registrations.

     (c)  On and after the Conversion Date (as defined in the Company's 
Amended and Restated Declaration of Trust), so long as the Investor and its 
Affiliates hold at least 25% of the Registrable Shares, if the Company 
proposes to register any of its common equity securities or any securities 
convertible into its common equity securities under the Securities Act (other 
than pursuant to (i) a registration statement filed pursuant to Rule 415 
under the Securities Act, (ii) a registration on Form S-4 or any successor 
form, or (iii) an offering of securities in connection with an employee 
benefit, share dividend, share ownership or dividend reinvestment plan) and 
the registration form to be used may be used for the registration of 
Registrable Shares, the Company will give prompt written notice to all 
holders of Registrable Shares of its intention to effect such a registration 
(each a "Piggyback Notice") and, subject to subparagraph 3(c) below, the 
Company will include in such registration all Registrable Shares with respect 
to which the Company has received written requests for inclusion therein 
within ten days after the date of sending the Piggyback Notice (a "Piggyback 
Registration"), unless, if the Piggyback Registration is not an underwritten 
offering, the Company in its reasonable judgement determines that, or in the 
case of an underwritten Piggyback Registration, the managing underwriters 
advise the Company in writing that in their opinion, the inclusion of 
Registrable Shares would adversely interfere with such offering, affect the 
Company's securities in the public markets, or otherwise adversely affect the 
Company.  Nothing herein shall affect the right of the Company to withdraw 
any such 

                                        4

<PAGE>

registration in its sole discretion.

     (d)  If a Piggyback Registration is a primary registration on behalf of 
the Company and, if the Piggyback Registration is not an underwritten 
offering, the Company in its reasonable judgement determines that, or in the 
case of an underwritten Piggyback Registration, the managing underwriters 
advise the Company in writing that in their opinion, the number of securities 
requested to be included in such registration exceeds the number which can be 
sold in an orderly manner within a price range acceptable to the Company, the 
Company will include in such registration (i) first, the securities the 
Company proposes to sell and (ii) second, the Registrable Shares requested to 
be included in such Registration and any other securities requested to be 
included in such registration, pro rata among the holders of Registrable 
Shares requesting such registration and the holders of such other securities 
on the basis of the number of Shares requested for inclusion in such 
registration by each such holder.

     (e)  If a Piggyback Registration is a secondary registration on behalf 
of holders of the Company's securities other than the holders of Registrable 
Shares, and, if the Piggyback Registration is not an underwritten offering, 
the Company determines that, or in the case of an underwritten Piggyback 
Registration, the managing underwriters advise the Company in writing that in 
their opinion, the number of securities requested to be included in such 
registration exceeds the number which can be sold in an orderly manner in 
such offering within a price range acceptable to the holders initially 
requesting such registration, the Company will include in such registration 
the securities requested to be included therein by the holders requesting 
such registration and the Registrable Shares requested to be included in such 
registration, pro rata among the holders of securities requesting such 
registration on the basis of the number of Shares requested for inclusion in 
such registration by each such holder.

     (f)  In the case of an underwritten Piggyback Registration, the Company 
will have the right to select the investment banker(s) and manager(s) to 
administer the offering.  If requested by the underwriters for any 
underwritten offerings by Holders, under a registration requested pursuant to 
Section 2(a), the Company will enter into a customary underwriting agreement 
with such underwriters for such offering, to contain such representations and 
warranties by the Company and such other terms which are customarily 
contained in agreements of this type.  The Holders shall be a party to such 
underwriting agreement and may, at their option, require that any or all of 
the conditions precedent to the obligations of such underwriters under such 
underwriting agreement be conditions precedent to the obligations of Holders. 
 The Holders shall not be required to make any representations or warranties 
to or agreement with the Company or the underwriters other than 
representations, warranties or agreements regarding the Holders and the 
Holders' intended method of distribution and any other representation or 
warranties required by law.

     Section (i)    Registration Procedures.

     (g)  The Company shall promptly notify the Holders of the occurrence

                                        5

<PAGE>


of the following events:

          (i)  when any registration statement relating to the Registrable 
Shares or post-effective amendment thereto filed with the Commission has 
become effective;

          (ii) the issuance by the Commission of any stop order suspending 
the effectiveness of any registration statement relating to the Registrable 
Shares;

          (iii)     the suspension of an effective registration statement by 
the Company in accordance with the last paragraph of Section 2(a) hereof;

          (iv) the Company's receipt of any notification of the suspension of 
the qualification of any Registrable Shares covered by a registration 
statement for sale in any jurisdiction; and

          (v)  the existence of any event, fact or circumstance that results 
in a registration statement or prospectus relating to Registrable Shares or 
any document incorporated therein by reference containing an untrue statement 
of material fact or omitting to state a material fact required to be stated 
therein or necessary to make the statements therein not misleading during the 
distribution of securities.

     The Company agrees to use its reasonable best efforts to obtain the 
withdrawal of any order suspending the effectiveness of any such registration 
statement or any state qualification as promptly as possible. The Investor 
agrees by acquisition of the Registrable Shares that upon receipt of any 
notice from the Company of the occurrence of any event of the type described 
in Section 4(a)(ii), (iii), (iv) or (v) to immediately discontinue its 
disposition of Registrable Shares pursuant to any registration statement 
relating to such securities until the Investor's receipt of written notice 
from the Company that such disposition may be made.

     (h)  The Company shall provide to the Holders, at no cost to the 
Holders, a copy of the registration statement and any amendment thereto used 
to effect the Registration of the Registrable Shares, each prospectus 
contained in such registration statement or post-effective amendment and any 
amendment or supplement thereto and such other documents as the requesting 
Holders may reasonably request in order to facilitate the disposition of the 
Registrable Shares covered by such registration statement.  The Company 
consents to the use of each such prospectus and any supplement thereto by the 
Holders in connection with the offering and sale of the Registrable Shares 
covered by such registration statement or any amendment thereto.  The Company 
shall also file a sufficient number of copies of the prospectus and any 
post-effective amendment or supplement thereto with the New York Stock 
Exchange, Inc. (or, if the Common Shares are no longer listed thereon, with 
such other securities exchange or market on which the Common Shares are then 
listed) so as to enable the Holders to have the benefits of the prospectus 
delivery provisions of Rule 153 under the Securities Act.


                                        6

<PAGE>

     (i)  The Company agrees to use its reasonable best efforts to cause the 
Registrable Shares covered by a registration statement to be registered with 
or approved by such state securities authorities as may be necessary to 
enable the Holders to consummate the disposition of such shares pursuant to 
the plan of distribution set forth in the registration statement; provided, 
however, that the Company shall not be obligated to take any action to effect 
any such Registration, qualification or compliance pursuant to this Section 4 
in any particular jurisdiction in which the Company would be required to 
execute a general consent to service of process in effecting such 
Registration, qualification or compliance unless the Company is already 
subject to service in such jurisdiction.

     (j)  Subject to the Company's Suspension Right, if any event, fact or 
circumstance requiring an amendment to a registration statement relating to 
the Registrable Shares or supplement to a prospectus relating to the 
Registrable Shares shall exist, immediately upon becoming aware thereof the 
Company agrees to notify the Holders and prepare and furnish to the Holders a 
post-effective amendment to the registration statement or supplement to the 
prospectus or any document incorporated therein by reference or file any 
other required document so that, as thereafter delivered to the purchasers of 
the Registrable Shares, the prospectus will not contain an untrue statement 
of a material fact or omit to state any material fact required to be stated 
therein or necessary to make the statements therein not misleading.

     (k)  The Company agrees to use its reasonable best efforts (including 
the payment of any listing fees) to obtain the listing of all Registrable 
Shares covered by the registration statement on each securities exchange on 
which securities of the same class or series are then listed.

     (l)  The Company agrees to use its reasonable best efforts to comply 
with the Securities Act and the Exchange Act in connection with the offer and 
sale of Registrable Shares pursuant to a registration statement, and, as soon 
as reasonably practicable following the end of any fiscal year during which a 
registration statement effecting a Registration of the Registrable Shares 
shall have been effective, to make available to its security holders an 
earnings statement satisfying the provisions of Section 11 (a) of the 
Securities Act.

     (m)  The Company agrees to cooperate with the selling Holders to 
facilitate the timely preparation and delivery of certificates representing 
Registrable Shares to be sold pursuant to a Registration and not bearing any 
Securities Act legend; and enable certificates for such Registrable Shares to 
be issued for such numbers of shares and registered in such names as the 
Holders may reasonably request at least two business days prior to any sale 
of Registrable Shares.

     Section (i)    Expenses of Registration.  The Company shall pay all 
Registration Expenses incurred in connection with the registration, 
qualification or compliance pursuant to Sections 2, 3 and 4 hereof.  All 
Selling Expenses incurred in connection with the sale of Registrable Shares 
by any of the Holders shall be borne by the Holder selling such Registrable 
Shares.  Each Holder shall pay the expenses of its own counsel.

                                        7
<PAGE>

     Section (ii)   Indemnification.

     (n)  The Company will indemnify each Holder, each Holder's officers and 
directors, and each person controlling such Holder within the meaning of 
Section 15 of the Securities Act, against all expenses, claims, losses, 
damages and liabilities (including reasonable legal expenses), arising out of 
or based on any untrue statement (or alleged untrue statement) of a material 
fact contained in any registration statement or prospectus relating to the 
Registrable Shares, or any amendment or supplement thereto, or based on any 
omission (or alleged omission) to state therein a material fact required to 
be stated therein or necessary to make the statements therein not misleading, 
provided, however, that the Company will not be liable in any such case to 
the extent that any such claim, loss, damage, liability or expense arises out 
of or is based on any untrue statement or omission or alleged untrue 
statement or omission, made in reliance upon and in conformity with 
information furnished in writing to the Company by such Holder or underwriter 
for inclusion therein.


                                        8
<PAGE>


     (o)  Each Holder will indemnify the Company, each of its trustees and 
each of its officers who sips the registration statement, each underwriter, 
if any, of the Company's securities covered by such registration statement, 
and each person who controls the Company or such underwriter within the 
meaning of Section 15 of the Securities Act, against all claims, losses, 
damages and liabilities (including reasonable legal fees and expenses) 
arising out of or based on any untrue statement (or alleged untrue statement) 
of a material fact contained in any such registration statement or 
prospectus, or any amendment or supplement thereto, or based on any omission 
(or alleged omission) to state therein a material fact required to be stated 
therein or necessary to make the statements therein not misleading, in each 
case to the extent, but only to the extent, that such untrue statement (or 
alleged untrue statement) or omission (or alleged omission) is made in such 
registration statement or prospectus, in reliance upon and in conformity with 
information furnished in writing to the Company by such Holder for inclusion 
therein.

     (p)  Each party entitled to indemnification under this Section 6 (the 
"Indemnified Party") shall give notice to the party required to provide 
indemnification (the "Indemnifying Party") promptly after such Indemnified 
Party has actual knowledge of any claim as to which indemnity may be sought, 
but the omission to so notify the Indemnifying Party shall not relieve it 
from any liability which it may have to the Indemnified Party pursuant to the 
provisions of this Section 6 except to the extent of the actual damages 
suffered by such delay in notification.  The Indemnifying Party shall assume 
the defense of such action, including the employment of counsel to be chosen 
by the Indemnifying Party to be reasonably satisfactory to the Indemnified 
Party, and payment of expenses.  The Indemnified Party shall have the right 
to employ its own counsel in any such case, but the legal fees and expenses 
of such counsel shall be at the expense of the Indemnified Party, unless the 
employment of such counsel shall have been authorized in writing by the 
Indemnifying Party in connection with the defense of such action, or the 
Indemnifying Party shall not have employed counsel to take charge of the 
defense of such action or the Indemnified Party shall have reasonably 
concluded that there may be defenses available to it or them which are 
different from or additional to those available to the Indemnifying Party (in 
which case the Indemnifying Party shall not have the right to direct the 
defense of such action on behalf of the Indemnified Party), in any of which 
events such fees and expenses shall be borne by the Indemnifying Party.  No 
Indemnifying Party, in the defense of any such claim or litigation, shall, 
except with the consent of each Indemnified Party, consent to entry of any 
judgment or enter into any settlement which does not include as an 
unconditional term thereof the giving by the claimant or plaintiff to such 
Indemnified Party of a release from all liability in respect to such claim or 
litigation.

                                        9

<PAGE>

     (q)  If the indemnification provided for in this Section 6 is 
unavailable to a party that would have been an Indemnified Party under this 
Section 6 in respect of any expenses, claims, losses, damages and liabilities 
referred to herein, then each party that would have been an Indemnifying 
Party hereunder shall, in lieu of indemnifying such Indemnified Party, 
contribute to the amount paid or payable by such Indemnified Party as a 
result of such expenses, claims, losses, damages and liabilities in such 
proportion as is appropriate to reflect the relative fault of the 
Indemnifying Party on the one hand and such Indemnified Party on the other in 
connection with the statement or omission which resulted in such expenses, 
claims, losses, damages and liabilities, as well as any other relevant 
equitable considerations.  The relative fault shall be determined by 
reference to, among other things, whether the untrue or alleged untrue 
statement of a material fact or the omission or alleged omission to state a 
material fact relates to information supplied by the Indemnifying Party or 
such Indemnified Party and the parties' relative intent, knowledge, access to 
information and opportunity to correct or prevent such statement or omission. 
 The Company and each Holder agree that it would not be just and equitable if 
contribution pursuant to this Section were determined by pro rata allocation 
or by any other method of allocation which does not take account of the 
equitable considerations referred to above in this Section 6(d).

     (r)  No person guilty of fraudulent misrepresentation (within the 
meaning of Section I I (f) of the Securities Act) shall be entitled to 
contribution from any person who was not guilty of such fraudulent 
misrepresentation.

     (s)  In no event shall any Holder be liable for any expenses, claims, 
losses, damages or liabilities pursuant to this Section 6 in excess of the 
net proceeds to such Holder of any Registrable Shares sold by such Holder.

     Section (i)    Information to be Furnished by  Holders.  Each Holder 
shall furnish to the Company such information as the Company may reasonably 
request and as shall be required in connection with the Registration and 
related proceedings referred to in Section 2 or Section 3 hereof.  If any 
Holder fails to provide the Company with such information within IO days of 
receipt of the Company's request, the Company's obligations under Section 2 
or Section 3 hereof, as applicable, with respect to such Holder or the 
Registrable Shares owned by such Holder shall be suspended until such Holder 
provides such information.

     Section (ii)   Undertaking to Participate in Underwriting.  If the 
Holders of at least $20 million of the Registrable Shares shall propose to 
sell Registrable Shares in an underwritten public offering, the Company shall 
make available members of the management of the Company and its affiliates 
for reasonable assistance in selling efforts relating to such offering, to 
the extent customary for a public offering (including, without limitation, to 
the extent customary, senior management attendance at due diligence meetings 
with the underwriters and their counsel and road shows) and shall enter into 
underwriting agreements containing usual and customary terms and conditions 
reasonably acceptable to the Company for such types of offerings.

     Section (iii)  Rule 144 Sales.

                                       10

<PAGE>


     (t)  The Company covenants that it will file the reports required to be 
filed by the Company under the Exchange Act, so as to enable any Holder to 
sell Registrable Shares pursuant to Rule 144 under the Securities Act.

     (u)  In connection with any sale, transfer or other disposition by any 
Holder of any Registrable Shares pursuant to Rule 144 under the Securities 
Act, the Company shall cooperate with such Holder to facilitate the timely 
preparation and delivery of certificates representing Registrable Shares to 
be sold and not bearing any Securities Act legend, and enable certificates 
for such Registrable Shares to be for such number of shares and registered in 
such names as the selling Holder may reasonably request at least two business 
days prior to any sale of Registrable Shares.

     Section (i)    Miscellaneous.

     (v)  Governing Law.  This Agreement shall be governed in all respects by 
the laws of the State of Maryland.  

     (w)  Entire Agreement.  This Agreement constitutes the full and entire 
understanding and agreement between the parties with regard to the subject 
matter hereof.

     (x)  Amendment.  No supplement, modification, waiver or termination of 
this Agreement shall be binding unless executed in writing by the party to be 
bound thereby.

     (y)  Notices, etc.  Each notice, demand, request, request for approval, 
consent, approval, disapproval, designation or other communication (each of 
the foregoing being referred to herein as a notice) required or desired to be 
given or made under this Agreement shall be in writing (except as otherwise 
provided in this Agreement), and shall be effective and deemed to have been 
received (i) when delivered in person, (ii) when sent by fax with receipt 
acknowledged, (iii) five (5) days after having been mailed by certified or 
registered United States mail, postage prepaid, return receipt requested, or 
(iv) the next business day after having been sent by a nationally recognized 
overnight mail or courier service, receipt requested.  Notices shall be 
addressed as follows: (a) if to the Investor, at the Investor's address or 
fax number set forth below its signature hereon, or at such other address or 
fax number as the Investor shall have furnished to the Company in writing, or 
(b) if to any assignee or transferee of an Investor, at such address or fax 
number as such assignee or transferee shall have furnished the Company in 
writing, or (c) if to the Company, at the address of its principal executive 
offices and addressed to the attention of the President, or at such other 
address or fax number as the Company shall have furnished to the Investors or 
any assignee or transferee.  Any notice or other communication required to be 
given hereunder to a Holder in connection with a registration may instead be 
given to the designated representative of such Holder.

     (z)  Counterparts.  This Agreement may be executed in any number of 
counterparts, each of which may be executed by fewer than all of the parties 
hereto (provided that each party 


                                       11

<PAGE>

executes one or more counterparts), each of which shall be enforceable 
against the parties actually executing such counterparts, and all of which 
together shall constitute one instrument.

     (aa) Severability.  In the event that any provision of this Agreement 
becomes or is declared by a court of competent jurisdiction to be illegal, 
unenforceable or void, this Agreement shall continue in full force and effect 
without said provision.

     (bb) Section Titles.  Section titles are for descriptive purposes only 
and shall not control or alter the meaning of this Agreement as set forth in 
the text.

     (cc) Successors and Assigns.  This Agreement shall be binding upon the 
parties hereto and their respective successors and assigns.

     (dd) Remedies.  The Company and the Investor acknowledge that there 
would be no adequate remedy at law if any party fails to perform any of its 
obligations hereunder, and accordingly agree that the Company and each 
Holder, in addition to any other remedy to which it may be entitled at law or 
in equity, shall be entitled to compel specific performance of the 
obligations of another party under this Agreement in accordance with the 
terms and conditions of this Agreement in any court of the United States or 
any State thereof having jurisdiction.

     (ee) Attorneys' Fees.  If the Company or any Holder brings an action to 
enforce its rights under this Agreement, the prevailing party in the action 
shall be entitled to recover its costs and expenses, including, without 
limitation, reasonable attorneys' fees, incurred in connection with such 
action, including any appeal of such action.

                            [signature page follows]


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<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as 
of the date first above written.

                                   PRIME GROUP REALTY TRUST


                                   By:
                                       --------------------------------------
                                   Name:                                    
                                         ------------------------------------
                                   Title:                                   
                                          -----------------------------------


                                   SECURITY CAPITAL PREFERRED GROWTH
                                   INCORPORATED


                                   By:                                      
                                       --------------------------------------
                                   Name:                                    
                                         ------------------------------------
                                   Title:                                   
                                          -----------------------------------












                                       13

<PAGE>
                                    EXHIBIT C

                               TAG-ALONG AGREEMENT

     THIS TAG-ALONG AGREEMENT (the "Agreement") dated as of November    , 
1997 is among Prime Financing, L.P., Prime Group Limited Partnership, Prime 
Group II, L.P., Prime Group III, L.P., Prime Group IV, L.P., Prime Group V, 
L.P., The Prime Group, Inc., PG/Primestone, L.L.C., a Delaware limited 
liability company (together with their respective controlled Affiliates and 
their successors in interest pursuant to Section 4 hereof, the "Other 
Holders"), and Security Capital Preferred Growth Incorporated, a Maryland 
corporation (together with its successors in interest pursuant to Section 4 
hereof, "SCPG").

                              PRELIMINARY STATEMENT

     WHEREAS the Other Holders own Common Units, which interests, subject to 
certain conditions, are exchangeable for Common Shares.

     WHEREAS SCPG owns the Preferred Shares, which shares, subject to certain 
conditions, are convertible into Common Shares.

     WHEREAS the Other Holders and SCPG desire to enter into this Agreement 
to set forth certain agreements with respect to certain transfers by the 
Other Holders of their Common Shares; and

     WHEREAS the execution and delivery of this Agreement by the parties 
hereto is a condition to the closing of the Series A Preferred Securities 
Purchase Agreement, dated as of November 11, 1997, by and among Prime Group 
Realty Trust, Prime Group Realty, L.P. and SCPG.

     NOW THEREFORE, in consideration of the foregoing and other good and 
valuable consideration, the receipt and sufficiency of which is hereby 
acknowledged, the parties agree as follows:

1.   Definitions.  As used in this Agreement, the following terms shall have 
the following meanings:

          "Affiliate" means, with respect to any Person, any other Person 
directly or indirectly controlling, controlled by or under direct or indirect 
common control with the first Person and shall include any Person who is an 
officer, director or beneficial holder of at least 10% of the then 
outstanding capital stock (or other shares of beneficial interest or 
partnership interest) of the first Person entitled ordinarily to vote for the 
first Person's directors (or, for persons that are not corporations, for 
those Persons exercising functions similar to directors of a corporation) and 
immediate family members of any such officer, director or holder.

<PAGE>

          "Common Shares" means the common shares of beneficial interest, 
$.01 par value per share, of Prime Group Realty Trust and Common Share 
Equivalents.

          "Common Share Equivalents" means any security that is convertible 
into or exchangeable for Common Shares or upon the exercise of which Prime 
Group Realty Trust is required to issue Common Shares, whether or not such 
securities are then convertible, exchangeable or exercisable.

          "Common Units" means the common units of limited partner interest 
of Prime Group Realty, L.P.

          "Extraordinary Transaction" means (a) any merger, consolidation, 
recapitalization, other business combination or other similar action for 
which approval of the holders of Common Shares is required and has been 
obtained, or (b) any other Transfer (whether, pursuant to an exchange or 
tender offer or otherwise) involving the sale or disposition of 80% or more 
of the then outstanding Common Shares.

          "Person" means any corporation, limited liability company, 
partnership, association, organization, trust, individual, government or any 
agency or political subdivision thereof, or other entity.

          "Preferred Shares" means the shares of Series A cumulative 
convertible preferred shares of beneficial interest, $.01 par value per share 
of Prime Group Realty Trust.

          "Sale" means any Transfer by the Other Holders or by Primestone 
Investment Partners, L.P. of Common Shares, directly or indirectly, to one or 
more Persons who are not Affiliates controlled by the Other Holders if, after 
giving effect to such Transfer and all prior Transfers of Common Shares 
during the preceding 12 months, the Other Holders and Primestone Investment 
Partners, L.P. will have Transferred more than 15% of the number of Common 
Shares beneficially owned by the Other Holders and Primestone Investment 
Partners, L.P., in the aggregate, at the beginning of such 12-month period 
(as adjusted for stock splits or stock dividends, or in connection with a 
combination of shares, recapitalization, merger, consolidation or other 
reorganization); provided, however, that the term "Sale" shall not apply to 
Transfers by Primestone Investment Partners, L.P., the proceeds of which are 
used either (a) to repay margin loan indebtedness of Primestone Investment 
Partners, L.P. or (b) to fund distributions to affiliates of The Blackstone 
Group.

          "Sale Notice" shall have the meaning ascribed to such term in 
Section 2(a) of this Agreement.

          "Securities Act" means the Securities Act of 1933, as amended from 
time to time.

          "Terms Notice" shall have the meaning ascribed to such term in 
Section 2(b) of 

                                        2

<PAGE>

this Agreement.

          "Tag-Along Rights" shall have the meaning ascribed to such term in 
Section 2 of this Agreement.

     "Transfer" means any direct or indirect sale, transfer, distribution, 
assignment, bequest, pledge, hypothecation, encumbrance, grant of a security 
interest in, or grant, issuance, sale or conveyance of an option, warrant or 
right to acquire, or other disposition of, one or more Common Shares; 
provided, however, that a Transfer shall not include (i) sales or 
dispositions made pursuant to a broadly distributed, underwritten public 
offering pursuant to an effective registration statement under the Securities 
Act, (ii) any pledge (including any foreclosure or seizure resulting from 
such pledge) to a bona fide financial institution or other business 
organization with a net worth in excess of $25 million for the purpose of 
securing bona fide indebtedness (including any guarantee or other obligation 
related thereto) of the Other Holders or (iii) sales or dispositions pursuant 
to an Extraordinary Transaction.

     "Transferee" means the recipient, directly or indirectly, of one or more 
Common Shares or any interest therein pursuant to a Transfer.

2.   Sale of Common Shares.  The Other Holders agree, that in the event that 
the Other Holders wish to engage in a Sale, to offer to SCPG the right to 
participate in such sale in the manner and on the terms set forth in this 
Section 2 (the rights of SCPG to participate in a Sale of Common Shares 
hereunder are referred to herein as the "Tag-Along Rights").

     (a)  Offer.  At least three business days prior to any Sale, the Other 
Holders shall deliver a written notice (the "Sale Notice") to SCPG which 
shall include:

          (i)  A description of the proposed Sale, specifying in reasonable 
detail the proposed terms and conditions of the proposed Sale, including the 
number of Common Shares proposed to be transferred as a result of such Sale, 
the purchase price (or liquidation value) of such Shares, the name and 
address of the proposed transferee(s), and the closing date of the proposed 
Sale.

          (ii) An offer by the Other Holders to include in the proposed Sale 
to the proposed transferee, at the option of SCPG, on the same terms and 
conditions as the proposed Sale, up to one Common Share for each two Common 
Shares to be sold by the Other Holders in the proposed Sale.

     (b)  Notice of Proposed Sale.  The Other Holders shall notify SCPG in 
writing (the "Terms Notice") of the terms of the Sale as soon as practicable 
after such terms are determined, but in any event at least one business day 
prior to the Sale.

     (c)  Time and Manner of Exercise.  If SCPG desires to accept the offer 
contained in 

                                        3

<PAGE>

the Sale Notice, it shall notify the Other Holders in writing before 5:00 
p.m. Chicago time on the business day following the date of receipt of the 
Terms Notice, which notice shall specify the number of Common Shares for 
which such offer has been accepted.  If SCPG has not so accepted such offer 
in writing it shall be deemed to have waived all of its Tag-Along Rights with 
respect to the proposed Sale, and the Other Holders shall be free, for a 
period of 90 days from and after the date of receipt by SCPG of the Terms 
Notice, to transfer the Common Shares specified in the Sale Notice but only 
on terms no more favorable to the Other Holders than the terms described in 
the Sale Notice and the Terms Notice, and any sale in violation of this 
provision shall be invalid.

     (d)  Other Agreements.

          (i)  The Other Holders shall use their best efforts to obtain the 
agreement of the prospective transferees) to the participation of SCPG in any 
contemplated Sale, and the Other Holders shall not transfer any of their 
Common Shares to the prospective transferee(s) if the prospective 
transferees) declines to allow the participation of SCPG as contemplated by 
this Section 2, and any sale in violation of this provision shall be invalid. 
 If SCPG elects to exercise its Tag-Along Rights hereunder, SCPG shall take 
such actions and execute such documents and instruments as may be requested 
by the Other Holders and as shall be reasonably necessary in order to 
consummate the proposed Sale on the same terms as the Other Holders.  Each of 
the Other Holders and SCPG shall bear their or its own costs and expenses 
incurred in connection with any proposed Sale.

          (ii) Prime Group Realty Trust agrees that, if requested by SCPG in 
writing, it will accelerate, pursuant to Section 3 of the Declaration 
creating the Preferred Shares, the date on which the Preferred Shares are 
convertible so as to permit SCPG to sell such number of Common Shares that it 
has elected to sell pursuant to Section 2 of this Agreement.

          (iii)     PG/Primestone, L.L.C., as managing general partner of 
Primestone Investment Partners, L.P., shall not vote for or consent to (and 
none of the Other Holders shall vote or cause any of their Affiliates to vote 
for or consent to) any sale of Common Shares by Primestone Investment 
Partners, L.P. (except with respect to Transfers described in the proviso to 
the definition of "Sale" in Section I hereof) unless in connection with such 
Transfer, SCPG is granted Tag-Along Rights in accordance with Section 2 
hereof.

     (e)  Abandonment of Sale.  The Other Holders shall have the right, in 
their sole discretion, at all times prior to consummation of the proposed 
Sale to abandon, rescind annul, withdraw or otherwise terminate such Sale, 
and the Other Holders shall not have any liability or obligation to SCPG with 
respect thereto by virtue of such abandonment, rescission, annulment, 
withdrawal or termination.

3.   Form of Agreement Satisfactory to SCPG.  Any agreement which SCPG may be 
requested or required to execute in connection with Section 2 hereof must be 
in form and substance reasonably satisfactory to SCPG.  No provision in this 
Agreement, including, without 

                                        4

<PAGE>

limitation, Section 2 hereof, shall require SCPG to make any representation 
(other than as to title, due authorization and enforceability relating solely 
to SCPG) or provide any indemnification in any such agreement (other than 
indemnification for breaches of the representations set forth in the 
preceding clause) and no right or obligation of SCPG shall be conditioned 
upon the making of such representation or the provision of such 
indemnification.

4.   Miscellaneous.

     (a)  Notices.  Notices and other communications provided for in this 
Agreement shall be in writing and shall be either delivered by reputable 
courier service (charges prepaid), sent by confirmed facsimile transmission 
or sent by certified mail (postage prepaid and return receipt requested) 
addressed to the party or parties sought to be charged with notice of the 
same at the respective addresses set forth below, subject to written notice 
of change of address given by any party to the other parties:

          IF TO THE OTHER
          HOLDERS:            The Prime Group, Inc.
                              77 West Wacker, Suite 3900 
                              Chicago, Illinois 60601
                              Attention:     Michael W. Reschke 
                                             Robert J. Rudnik
                              Fax: (312) 917-1511

          with a copy to:     Wayne D. Boberg
                              Winston & Strawn
                              35 West Wacker Drive
                              Chicago, Illinois 60601
                              Fax: (312) 558-5700

          IF TO SCPG:         Security Capital Preferred Growth  Incorporated
                              11 South LaSalle Street
                              Chicago, Illinois 60603
                              Attention:     Daniel F. Miranda 
                                             David E. Rosenbaum 
                                             Joshua D. Goldman
                              Fax: (312) 345-5888

          with a copy to:     Mayer, Brown & Platt
                              190 South LaSalle Street
                              Chicago, Illinois 60603
                              Attention:     Philip J. Niehoff, Esq.
                              Fax: (312) 701-7711

                                        5

<PAGE>

     Notice shall be effective and deemed to have been received (i) when 
delivered in person, (ii) when sent by fax with receipt acknowledged, (iii) 
five (5) days after having been mailed by certified or registered United 
States mail, postage prepaid, return receipt requested, or (iv) the next 
business day after having been sent by a nationally recognized overnight mail 
or courier service, receipt requested.

     (b)  Changes and Modifications; Termination, Actions under this 
Agreement.  This Agreement may be terminated, changed, modified or extended, 
and consents hereunder may be granted, only by an agreement in writing signed 
by SCPG and the owners of a majority of the Common Shares owned by the Other 
Holders.

     (c)  Complete Agreement.  This Agreement embodies the complete agreement 
and understanding among the parties and supersedes and preempts any prior 
understandings, agreements, or representations by or among the parties, 
written or oral, which may have related to the subject matter hereof in any 
way.  This Agreement shall be binding upon and inure to the benefit of the 
parties hereto and their respective successors and assigns (including, 
without limitation, successor holders of Shares); provided, however, that 
SCPG may not assign or transfer its rights or obligations hereunder without 
the prior written consent of the owners of a majority of the Common Shares 
held by the Other Holders, except to one or more Persons of the types 
specified in Section 8.2 of the Purchase Agreement.

     (d)  Counterparts.  This Agreement may be executed in counterparts, each 
of which shall be deemed an original, but all of which taken together shall 
constitute one instrument.

     (e)  Severability.  If in any judicial proceeding a court shall refuse 
to enforce any provision of this Agreement, then such unenforceable provision 
shall be deemed eliminated from this Agreement for the purpose of such 
proceeding to the extent necessary to permit the remaining provisions to be 
enforced.

     (f)  Governing Law.  This Agreement shall be governed by the laws of the 
State of Maryland without giving effect to the conflict of laws rules of any 
jurisdiction.

     (g)  Remedies.  The parties hereto shall have all remedies for breach of 
this Agreement available to them provided by law or equity.  Without limiting 
the generality of the foregoing, the parties agree that in addition to all 
other rights and remedies available at law or in equity, the parties shall be 
entitled to obtain specific performance of the obligations of each party to 
this Agreement and immediate injunctive relief, and that in the event any 
action or proceeding is brought in defense, that there is an inadequate 
remedy at law.

     (h)  Transfers.  It shall be a condition to any Transfer of Common 
Shares to Affiliates of Michael W. Reschke that the Transferee agree in 
writing to be bound by the obligations of the Other Holders pursuant to, and 
as provided in, this Agreement, whereupon such Transferee shall be deemed to 
be a successor in interest of the Other Holders for all purposes of this 
Agreement 

                                        6

<PAGE>

(but which subsequent agreement shall not relieve the Other Holders of their 
obligations hereunder).  Any Transfer in violation of this provision shall be 
void.

     (i)  Termination.  This Agreement shall terminate on the date on which 
SCPG shall cease to own Common Shares issued or issuable upon conversion or 
exchange of the Preferred Shares representing at least five percent of the 
then outstanding Common Shares (on a fully diluted basis).

                             [Signature Page Follows]











                                       7
                                         
<PAGE>

     IN WITNESS WHEREOF, the parties have executed this Agreement as of the 
date set forth above.

                                   ------------------------------------------
                                                                            
                                   Michael W. Reschke



                                   PRIME GROUP REALTY TRUST



                                   By: --------------------------------------
                                   Its: -------------------------------------



                                   PRIME GROUP REALTY, L.P.

                                   By:  Prime Group Realty Trust, its
                                        managing general partner


                                   By: --------------------------------------
                                   Its: -------------------------------------



                                   PRIME GROUP II, L.P., PRIME GROUP III,
                                   L.P., PRIME GROUP IV, L.P., PRIME GROUP
                                   V, L.P.

                                   By:  PGLP, Inc., its sole General
                                        Partner



                                   By: --------------------------------------
                                   Its: -------------------------------------



                                   PRIME GROUP LIMITED PARTNERSHIP


                                   ------------------------------------------
                                   By:  Michael W. Reschke, its Managing
                                        General Partner          



<PAGE>



                                   PRIME FINANCING, L.P.

                                   By:  Prime Financing, Inc., its sole
                                        General Partner


                                   By: --------------------------------------
                                   Its: -------------------------------------



                                   THE PRIME GROUP, INC.



                                   By: --------------------------------------
                                   Its: -------------------------------------



                                   PG/PRIMESTONE, L.L.C.



                                   By: --------------------------------------
                                   Its: -------------------------------------



                                   SECURITY CAPITAL PREFERRED GROWTH
                                   INCORPORATED



                                   By: --------------------------------------
                                   Its: -------------------------------------


 

<PAGE>

ACCEPTED AND AGREED TO
WITH RESPECT TO SECTION 2(d)(ii):

Prime Group Realty, L.P.

By:  Prime Group Realty Trust, its 
     managing general partner


By: -----------------------------------
Name: ---------------------------------
Its: ----------------------------------


PRIME GROUP REALTY TRUST


By: -----------------------------------
Name: ---------------------------------
Its: ----------------------------------

 

<PAGE>

                                   EXHIBIT D


                                November    , 1997




Security Capital Markets Group Incorporated
399 Park Avenue
New York, New York 10022
Attention:  Mr. Garret C. House, Vice President

     Re:  Prime Group Realty Trust

Gentlemen:

     This letter confirms the appointment of Security Capital Markets Group 
Incorporated ("SCMG") by Prime Group Realty Trust (the "Company") and Prime 
Group Realty, L.P. (the "Operating Partnership") as a Placement Agent in 
connection with that certain Series A Preferred Securities Purchase Agreement 
(the "Purchase Agreement") by and among the Company, the Operating 
Partnership and Security Capital Preferred Growth Incorporated ("SCPG"), 
pursuant to which SCPG is purchasing 2 million shares of the Company's Series 
A Cumulative Convertible Preferred Shares of Beneficial Interest (the 
"Securities").  Nothing herein shall constitute an undertaking by SCMG to 
underwrite or otherwise purchase the Securities.

     For these services, the Company and the Operating Partnership jointly 
agree that SCMG's compensation hereunder will consist of a fee (the "Fee") 
equal to 1% of the Aggregate Purchase Price (as defined in the Purchase 
Agreement) of all Securities purchased by SCPG pursuant to the Purchase 
Agreement.  Such fee shall be payable at or prior to the Closing Date (as 
defined in the Purchase Agreement).  The Company and the Operating 
Partnership agree and acknowledge that no fee payable to any other finder, 
broker, broker-dealer or other party shall reduce the Fee payable hereunder.

     Each of SCMG, the Company and the Operating Partnership agrees that (i) 
in connection with the sale of the Securities, neither it nor any person 
acting on its behalf has offered or sold or will offer or sell the Securities 
by any form of general solicitation or general advertising, including but not 
limited to the following: (A) any advertisement, article, notice or other 
communication published in any newspaper or broadcast over television or 
radio or (B) any seminar or meeting whose attendees were invited by any 
general solicitation or general advertising; and (ii) it has solicited and 
will solicit offers for Securities only from and will offer Securities only 
to, investors that it has a reasonable basis to believe are "accredited 
investors" within the meaning of Rule 501 (a) under the Securities Act of 
1933, as amended.

<PAGE>

 
     In consideration for SCMG agreeing to provide the services referred to 
herein, the Company and the Operating Partnership jointly agree to indemnify 
and hold harmless SCMG, its affiliates and each other entity or person, if 
any, controlling SCMG or any of its affiliates within the meaning of the 
federal securities laws, and their respective directors, officers and 
employees (SCMG and each such entity or person being referred to as an 
"Indemnified Person"), from and against any claim by any third party for any 
losses, claims, damages or liabilities (or actions in respect thereof) 
relating to or arising out of the services performed pursuant to this 
agreement, the purchase contemplated hereby or SCMG's role in connection 
therewith, and to reimburse any Indemnified Person for all expenses 
(including, without limitation, reasonable fees and disbursements of counsel) 
incurred in connection with any action, suit or proceeding in relation 
thereto or in connection therewith, other than any such losses, claims, 
damages, liabilities or expenses of any Indemnified Person that are 
determined by final judgment of a court of competent jurisdiction to have 
resulted primarily from actions taken or omitted to be taken by such 
Indemnified Person in bad faith or from such Indemnified Person's gross 
negligence or SCMG's intentional and material breach of this agreement. The 
Company shall not be liable for any settlement of any proceeding effected 
without its prior written consent, but if settled with such consent or if 
there be a final judgment for the plaintiff, the Company agrees to indemnify 
the Indemnified Person from and against any loss or liability by reason of 
such settlement or judgment subject to the rights of the Company in this 
paragraph to claim exemption from its indemnity obligations.  The Company 
shall not, without the prior written consent of any Indemnified Person, 
effect any settlement of any proceeding in respect of which such Indemnified 
Person is a party and indemnity could have been sought hereunder by such 
Indemnified Person, unless such settlement includes an unconditional release 
of such Indemnified Person from all liability on claims that are the subject 
matter of such proceeding.

     This agreement shall be governed by the internal laws of the state of 
Illinois.  This agreement may be terminated at any time by the Company or 
SCMG upon written notice to the other party; provided that the 
representations and indemnity obligations of the Company hereunder and the 
obligation of the Company to pay SCMG the Fee shall survive any termination 
of SCMG's engagement hereunder and any sale of such Securities. 

<PAGE>

     Please indicate your agreement with this understanding by signing the 
letter below and returning it to the undersigned.

                              Sincerely,

                              PRIME GROUP REALTY TRUST



                              By: ------------------------------------------
                              Name: ----------------------------------------
                              Its: -----------------------------------------


                              Prime Group Realty, L.P.

                              By:  Prime Group Realty Trust, its general
                                   partner 


                              By: ------------------------------------------
                              Name: ----------------------------------------
                              Its: -----------------------------------------


Accepted and Agreed to as of the date set forth above:

SECURITY CAPITAL MARKETS GROUP INCORPORATED



By: --------------------------------------
Name: ------------------------------------
Its: -------------------------------------