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                                                                    EXHIBIT 4.1

                             ARTICLES SUPPLEMENTARY
                                       OF
                        CORPORATE OFFICE PROPERTIES TRUST
                 SERIES F CUMULATIVE REDEEMABLE PREFERRED SHARES
                           (PAR VALUE $0.01 PER SHARE)

     CORPORATE OFFICE PROPERTIES TRUST, a Maryland real estate investment trust
(hereinafter called the "Trust"), having its principal office in Columbia,
Maryland, hereby certifies to the Department of Assessments and Taxation of the
State of Maryland that:

     FIRST: Pursuant to authority expressly vested in the Board of Trustees of
the Trust by Article VI of the Declaration of Trust of the Trust, as amended to
date (the "Declaration of Trust"), the Board of Trustees has duly classified
1,425,000 authorized but unissued preferred shares of beneficial interest of the
Trust, par value $0.01 per share (the "Preferred Shares"), into a series
designated as 9.875% Series F Cumulative Redeemable Preferred Shares, par value
$0.01 per share, and has provided for the issuance of such class by adoption of
a resolution in the form of Article Third hereof effective as of September 13,
2001.

     SECOND: The classification increases the number of shares classified as
9.875% Series F Cumulative Redeemable Preferred Shares, par value $0.01 per
share, from no shares immediately prior to the classification to 1,425,000
shares immediately after the classification. The classification decreases the
number of unclassified Preferred Shares from 1,425,307 to 307.

     THIRD: The terms of the 9.875% Series F Cumulative Redeemable Preferred
Shares (including the preferences, conversion or other rights, voting powers,
restrictions, limitations as to dividends and other distributions,
qualifications, or terms or conditions of redemption) as set by the Board of
Trustees are as follows:

     1. NUMBER OF SHARES AND DESIGNATION.

     This series of Preferred Shares shall be designated as 9.875% Series F
Cumulative Redeemable Preferred Shares, par value $0.01 per share (the "Series F
Preferred Shares"), and 1,425,000 shares shall be the authorized number of such
Series F Preferred Shares constituting such series.

     2. DEFINITIONS.

     For purposes of the Series F Preferred Shares, the following terms shall
have the meanings indicated:

     "Affiliate" of a Person means a Person that directly, or indirectly through
one or more intermediaries, controls or is controlled by, or is under common
control with, the Person specified.

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     "Board of Trustees" shall mean the Board of Trustees of the Trust or any
committee authorized by such Board of Trustees to perform any of its
responsibilities with respect to the Series F Preferred Shares; provided that,
for purposes of paragraph (a) of Section 8 of this Article, the term "Board of
Trustees" shall not include any such committee.

     "Business Day" shall mean any day other than a Saturday, Sunday or a day on
which state or federally chartered banking institutions in New York, New York
are not required to be open.

     "Code" shall mean the Internal Revenue Code of 1986, as amended from time
to time, or any successor statute thereto. Reference to any provision of the
Code shall mean such provision as in effect from time to time, as the same may
be amended, and any successor thereto, as interpreted by any applicable
regulations or other administrative pronouncements as in effect from time to
time.

     "Common Shares" shall mean the common shares of beneficial interest, par
value $0.01 per share, of the Trust.

     "Declaration of Trust" shall mean the Amended and Restated Declaration of
Trust of the Trust as filed for record with the State Department of Assessments
and Taxation of Maryland, and any amendments thereto.

     "Dividend Payment Date" shall mean January 15, April 15, July 15 and
October 15 of each year; provided, that if any Dividend Payment Date falls on
any day other than a Business Day, the dividend payment payable on such Dividend
Payment Date shall be paid on the Business Day immediately following such
Dividend Payment Date and no interest shall accrue on such dividend from such
date to such Dividend Payment Date.

     "Dividend Periods" shall mean the Initial Dividend Period and each
subsequent quarterly dividend period commencing on and including January 15,
April 15, July 15 and October 15 of each year and ending on and including the
day preceding the first day of the next succeeding Dividend Period, other than
the Dividend Period during which any Series F Preferred Shares shall be redeemed
pursuant to Section 5 hereof, which shall end on and include the Redemption Date
with respect to the Series F Preferred Shares being redeemed.

     "Dividend Record Date" shall have the meaning set forth in paragraph (a) of
Section 3 of this Article.

     "Equity Shares" shall mean shares of any class or series of shares of
beneficial ownership in the Trust.

     "Exchange Act" shall mean the Securities Exchange Act of 1934, as amended.

     "Initial Dividend Period" shall mean the period commencing on and including
the Issue Date and ending on and including October 14, 2001.

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     "Issue Date" is September 13, 2001.

     "Junior Shares" shall have the meaning set forth in paragraph (a) of
Section 7 of this Article.

     "Liquidation Preference" shall have the meaning set forth in paragraph (a)
of Section 4 of this Article.

     "Operating Partnership" shall mean Corporate Office Properties, L.P., a
Delaware limited partnership.

     "Parity Shares" shall have the meaning set forth in paragraph (b) of
Section 7 of this Article.

     "Person" shall mean an individual, corporation, partnership, estate, trust
(including a trust qualifying under Section 401(a) or 501(c)(17) of the Code), a
portion of a trust permanently set aside for or to be used exclusively for the
purposes described in Section 642(c) of the Code, association, "private
foundation," within the meaning of Section 509(a) of the Code, joint stock
company or other entity, and also includes a "group," as that term is used for
purposes of Section 13(d)(3) of the Exchange Act, and a group to which an
Excepted Holder Limit (as defined in Article VII of the Declaration of Trust)
applies.

     "Redemption Date" shall mean, in the case of any redemption of any Series F
Preferred Shares, the date fixed for redemption of such shares.

     "Redemption Notice" shall have the meaning set forth in paragraph (d) of
Section 5 of this Article.

     "Redemption Price" shall mean, with respect to any Series F Preferred
Shares to be redeemed, a cash payment equal to 100% of the Liquidation
Preference thereof plus all accrued and unpaid dividends, if any, to the
Redemption Date.

     "REIT" shall mean a "real estate investment trust," as defined in Section
856 of the Code.

     "Senior Shares" shall have the meaning set forth in paragraph (c) of
Section 7 of this Article.

     "Series A Preferred Shares" shall mean the Trust's 5.5% Series A
Convertible Preferred Shares of beneficial interest, par value $0.01 per share.

     "Series B Preferred Shares" shall meaning the Trust's 10% Series B
Cumulative Redeemable Preferred Shares of beneficial interest, par value $0.01
per share.

     "Series D Preferred Shares" shall mean the Trust's 4% Series D Cumulative
Convertible Redeemable Preferred Shares of beneficial interest, par value $0.01
per share.

     "Series E Preferred Shares" shall mean the Trust's 10.25% Series E
Cumulative Redeemable Preferred Shares of beneficial interest, par value $0.01
per share.

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     "Set apart for payment" shall be deemed to include, without any action
other than the following, the recording by the Trust in its accounting ledgers
of any accounting or bookkeeping entry which indicates, pursuant to a
declaration of dividends or other distribution by the Board of Trustees, the
allocation of funds to be so paid on any series or class of Equity Shares of the
Trust; provided, however, that if any funds for any class or series of Junior
Shares or any class or series of Parity Shares are placed in a separate account
of the Trust or delivered to a disbursing, paying or other similar agent, then
"set apart for payment" with respect to the Series F Preferred Shares shall mean
placing such funds in a separate account or delivering such funds to a
disbursing, paying or other similar agent.

     "Transfer Agent" means Wells Fargo & Company or such transfer agent as may
be designated from time to time by the Board of Trustees or its designee as the
transfer agent for the Series F Preferred Shares.

     "Trustee" shall mean a member of the Board of Trustees.

     "Voting Parity Shares" shall have the meaning set forth in paragraph (a) of
Section 8 of this Article.

     3. DIVIDENDS.

     (a) The holders of Series F Preferred Shares shall be entitled to receive,
when, as and if declared by the Board of Trustees, out of funds legally
available for that purpose, quarterly cash dividends on the Series F Preferred
Shares at the rate of 9.875% of the Liquidation Preference per year (equivalent
to $2.46875 per year per Series F Preferred Share). Such dividends shall be
cumulative from the Issue Date, whether or not in any Dividend Period or Periods
such dividends shall be declared or there shall be funds of the Trust legally
available for the payment of such dividends, and shall be payable quarterly in
arrears on each Dividend Payment Date, commencing on October 15, 2001. Each such
dividend shall be payable in arrears to the holders of record of the Series F
Preferred Shares, as they appear on the share records of the Trust at the close
of business on the applicable record date (the "DIVIDEND RECORD DATE"), which
shall be fixed by the Board of Trustees and which shall be not more than 60 days
nor less than 10 days prior to each such Dividend Payment Date. The Dividend
Record Date for the dividend payable on October 15, 2001 shall be September 30,
2001. Accrued and unpaid dividends for any past Dividend Periods may be declared
and paid at any time, without reference to any regular Dividend Payment Date, to
holders of record on such date, which date shall not precede by more than 45
days nor less than 15 days the payment date thereof, as may be fixed by the
Board of Trustees.

     (b) Any dividend payable on the Series F Preferred Shares for any partial
Dividend Period shall be computed ratably on the basis of twelve 30-day months
and a 360-day year. Holders of Series F Preferred Shares shall not be entitled
to any dividends in excess of full cumulative dividends, as herein provided, on
the Series F Preferred Shares. No interest, or sum of money in lieu of interest,
shall be payable in respect of any dividend payment or payments on the Series F
Preferred Shares that may be in arrears.

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     (c) So long as any of the Series F Preferred Shares are outstanding, when
dividends are not paid in full upon the Series F Preferred Shares or any other
class or series of Parity Shares, or a sum sufficient for such payment is not
set apart for payment, all dividends declared upon the Series F Preferred Shares
and any Parity Shares shall be declared ratably in proportion to the respective
amounts of dividends accrued and unpaid on the Series F Preferred Shares and
accrued and unpaid on such Parity Shares. Except as set forth in the preceding
sentence, unless dividends on the Series F Preferred Shares equal to the full
amount of accrued and unpaid dividends have been or contemporaneously are
declared and paid or declared and a sum sufficient for the payment thereof has
been or contemporaneously is set apart for such payment, for all past dividends
periods, no dividends shall be declared or paid or set apart for payment by the
Trust and no other distribution of cash or other property may be declared or
made, directly or indirectly, by the Trust with respect to any Parity Shares.

     (d) So long as any of the Series F Preferred Shares are outstanding, unless
dividends equal to the full amount of all accrued and unpaid dividends on the
Series F Preferred Shares have been paid, or declared and set apart for payment,
for all past dividend periods, no dividends (other than dividends or
distributions paid in Junior Shares or options, warrants or rights to subscribe
for or purchase Junior Shares) may be declared or paid or set apart for payment
by the Trust and no other distribution of cash or other property may be declared
or made, directly or indirectly, by the Trust with respect to any Junior Shares,
nor shall any Junior Shares be redeemed, purchased or otherwise acquired (except
for a redemption, purchase or other acquisition of Common Shares made for
purposes of an employee incentive or benefit plan of the Trust or a subsidiary
of the Trust) for any consideration (or any monies be paid to or made available
for a sinking fund for the redemption of any such Junior Shares), directly or
indirectly, by the Trust (except by conversion into or exchange for Junior
Shares, or options, warrants or rights to subscribe for or purchase Junior
Shares), nor shall any other cash or other property be paid or distributed to or
for the benefit of holders of Junior Shares.

     (e) Notwithstanding the provisions of this Section 3, the Trust shall not
be prohibited from (i) declaring or paying or setting apart for payment any
dividend or distribution on any Parity Shares or (ii) redeeming, purchasing or
otherwise acquiring any Parity Shares, in each case, if such declaration,
payment, redemption, purchase or other acquisition is necessary in order to
maintain the continued qualification of the Trust as a REIT under Section 856 of
the Code.

     4. LIQUIDATION PREFERENCE.

     (a) Upon any voluntary or involuntary liquidation, dissolution or
winding-up of the Trust, before any payment or distribution by the Trust shall
be made to or set apart for payment to the holders of any Junior Shares, the
holders of Series F Preferred Shares shall be entitled to receive a liquidation
preference of Twenty-Five Dollars ($25.00) per Series F Preferred Share (the
"LIQUIDATION PREFERENCE"), plus an amount equal to all accrued and unpaid
dividends (whether or not earned or declared) to the date of final distribution
to such holders; but such holders shall not be entitled to any further payment.
Until the holders of the Series F Preferred Shares have been paid the
Liquidation Preference in full, plus an amount equal to all accrued and unpaid
dividends (whether or not earned or declared) to the date of final distribution
to such holders, no payment will be made

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to any holder of Junior Shares upon the liquidation, dissolution or winding-up
of the Trust. If, upon any liquidation, dissolution or winding-up of the Trust,
the assets of the Trust, or proceeds thereof, distributable among the holders of
Series F Preferred Shares shall be insufficient to pay in full the Liquidation
Preference and liquidating payments on any other shares of any class or series
of Parity Shares, then such assets, or the proceeds thereof, shall be
distributed among the holders of Series F Preferred Shares and any such other
Parity Shares ratably in the same proportion as the respective amounts that
would be payable on such Series F Preferred Shares and any such other Parity
Shares if all amounts payable thereon were paid in full. For the purposes of
this Section 4, a voluntary or involuntary liquidation, dissolution or
winding-up of the Trust shall not include (i) a consolidation or merger of the
Trust with or into one or more other entities, (ii) a sale or transfer of all or
substantially all of the Trust's assets, or (iii) a statutory share exchange.

     (b) Upon any liquidation, dissolution or winding-up of the Trust, after
payment shall have been made in full to the holders of Series F Preferred Shares
and any Parity Shares, as provided in Section 4(a), any other series or class or
classes of Junior Shares shall, subject to the respective terms thereof, be
entitled to receive any and all assets remaining to be paid or distributed, and
the holders of the Series F Preferred Shares and any Parity Shares shall not be
entitled to share therein.

     5. REDEMPTION AT THE OPTION OF THE TRUST.

     (a) Series F Preferred Shares shall not be redeemable by the Trust prior to
October 15, 2006, except as set forth in Article VII of the Declaration of Trust
that is incorporated by reference herein. On or after October 15, 2006, the
Trust, at its option, may redeem Series F Preferred Shares, in whole or from
time to time in part, at the Redemption Price. The Redemption Price of the
Series F Preferred Shares (other than any portion thereof consisting of accrued
and unpaid dividends) shall be payable solely with the proceeds from the sale by
the Trust or the Operating Partnership of equity securities of the Trust or the
Operating Partnership (whether or not such sale occurs concurrently with such
redemption). For purposes of the preceding sentence, "equity securities" shall
include any Common Shares, preferred shares, depositary shares, partnership or
other interests, participations or other ownership interests (however
designated) and any rights (other than debt securities convertible into or
exchangeable at the option of the holder for equity securities of the Trust
(unless and to the extent such debt securities are subsequently converted into
such equity securities)) or options to purchase any of the foregoing of or in
the Trust or the Operating Partnership.

     (b) In the event of a redemption of Series F Preferred Shares, if the
Redemption Date occurs after a Dividend Record Date and on or prior to the
related Dividend Payment Date, the dividend payable on such Dividend Payment
Date in respect of such shares called for redemption shall be payable on such
Dividend Payment Date to the holders of record at the close of business on such
Dividend Record Date and shall not be payable as part of the Redemption Price
for such shares. If full cumulative dividends on all outstanding Series F
Preferred Shares have not been paid or declared and set apart for payment, no
Series F Preferred Shares may be redeemed unless all outstanding Series F
Preferred Shares are simultaneously redeemed and neither the Trust nor any
Affiliate of the Trust may purchase or acquire Series F Preferred Shares,
otherwise than pursuant to a purchase or exchange offer made on the same terms
to all holders of Series F Preferred Shares.

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     (c) If fewer than all the outstanding Series F Preferred Shares are to be
redeemed, the Trust will select those Series F Preferred Shares to be redeemed
pro rata in proportion to the numbers of Series F Preferred Shares held by
holders (with adjustment to avoid redemption of fractional shares) or by lot or
in such other manner as the Board of Trustees may determine. If fewer than all
Series F Preferred Shares represented by any certificate are redeemed, then a
new certificate representing the unredeemed Series F Preferred Shares shall be
issued without cost to the holders thereof.

     (d) If the Trust shall redeem Series F Preferred Shares pursuant to
paragraph (a) of this Section 5, notice of the redemption will be given by
publication in a newspaper of general circulation in the City of New York, such
publication to be made once a week for two consecutive weeks commencing not less
than 30 nor more than 60 days prior to the Redemption Date. A similar notice of
such redemption shall be mailed by the Trust not less than 30 days nor more than
60 days prior to the Redemption Date to each holder of record of the Series F
Preferred Shares to be redeemed (the "REDEMPTION NOTICE"). Such Redemption
Notice shall be provided by first class mail, postage prepaid, at such holder's
address as the same appears on the share records of the Trust. Neither the
failure to mail the Redemption Notice, nor any defect therein or in the mailing
thereof to any particular holder, shall affect the sufficiency of the Redemption
Notice or the validity of the proceedings for redemption with respect to the
other holders. A Redemption Notice which has been mailed in the manner herein
provided shall be conclusively presumed to have been duly given on the date
mailed whether or not the holder receives the Redemption Notice. Each Redemption
Notice shall state, as appropriate: (i) the Redemption Date; (ii) the number of
Series F Preferred Shares to be redeemed; (iii) the place or places where
certificates for such Series F Preferred Shares are to be surrendered; and (iv)
the Redemption Price payable on such Redemption Date, including, without
limitation, a statement as to whether or not accrued and unpaid dividends will
be (x) payable as part of the Redemption Price, or (y) payable on the next
Dividend Payment Date to the record holder at the close of business on the
relevant Record Date as described in the next succeeding sentence. A Redemption
Notice having been mailed as aforesaid, from and after the Redemption Date
(unless the Trust shall fail to make available the amount of cash necessary to
effect such redemption), (i) dividends on the Series F Preferred Shares so
called for redemption shall cease to accrue on said shares, (ii) said shares
shall no longer be deemed to be outstanding, and (iii) all rights of the holders
thereof as holders of Series F Preferred Shares shall cease, except (a) the
right to receive the Redemption Price, without interest thereon, and (b) if the
Redemption Date for any Series F Preferred Shares occurs after any Dividend
Record Date and on or prior to the related Dividend Payment Date, the full
dividend payable on such Dividend Payment Date in respect of such Series F
Preferred Shares called for redemption shall be payable on such Dividend Payment
Date to the holders of record of such shares at the close of business on the
corresponding Dividend Record Date notwithstanding the prior redemption of such
shares. The Trust's obligation to make available the cash necessary to effect
such redemption in accordance with the preceding sentence shall be deemed
fulfilled if, on or before the applicable Redemption Date, the Trust shall
irrevocably deposit in trust with a bank or trust company (which may not be an
Affiliate of the Trust) that has, or is an Affiliate of a bank or trust company
that has, a capital and surplus of at least $50,000,000, such amount of cash as
is necessary for such redemption plus, if such Redemption Date occurs after any
Dividend Record Date and on or prior to the related Dividend Payment Date, such
amount of cash as is necessary to pay the dividend payable on such Dividend
Payment Date in respect of such Series F

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Preferred Shares called for redemption, with irrevocable instructions that such
cash be applied to the redemption of the Series F Preferred Shares so called for
redemption and, if applicable, the payment of such dividend. No interest shall
accrue for the benefit of the holders of Series F Preferred Shares to be
redeemed on any cash so set aside by the Trust. Subject to applicable escheat
laws, any such cash unclaimed at the end of two years from the Redemption Date
shall revert to the general funds of the Trust, after which reversion the
holders of Series F Preferred Shares so called for redemption shall look only to
the general funds of the Trust for the payment of such cash. As promptly as
practicable after the surrender in accordance with the Redemption Notice of the
certificates for any such Series F Preferred Shares to be so redeemed (properly
endorsed or assigned for Transfer, if the Trust shall so require and the
Redemption Notice shall so state), such certificates shall be exchanged for cash
(without interest thereon) for which such Series F Preferred Shares have been
redeemed in accordance with such Redemption Notice.

     6. STATUS OF REACQUIRED SHARES.

     All Series F Preferred Shares that have been issued and are reacquired in
any manner by the Trust (including, without limitation, Series F Preferred
Shares which are redeemed) shall be returned to the status of authorized but
unissued Series F Preferred Shares.

     7. RANKING.

     The Series F Preferred Shares will, with respect to dividend rights and
rights upon the liquidation, dissolution or winding-up of the Trust, rank:

          (a) prior or senior to the Common Shares and any other class or series
     of the Trust's Equity Shares authorized or designated in the future if the
     holders of Series F Preferred Shares shall be entitled to the receipt of
     dividends or of amounts distributable upon liquidation, dissolution or
     winding-up in preference or priority to the holders of shares of such class
     or series ("JUNIOR SHARES");

          (b) on a parity with the Series A Preferred Shares, the Series B
     Preferred Shares, the Series D Preferred Shares, the Series E Preferred
     Shares and any other class or series of the Trust's Equity Shares
     authorized or designated in the future if, by the terms of such class or
     series, the holders of such class or series of securities and the Series F
     Preferred Shares shall be entitled to the receipt of dividends and of
     amounts distributable upon liquidation, dissolution or winding-up in
     proportion to their respective amounts of accrued and unpaid dividends per
     share or liquidation preferences, without preference or priority of one
     over the other ("PARITY SHARES"); and

          (c) junior to any class or series of our Equity Shares authorized or
     designated in the future if, by the terms of such class or series, the
     holders of such class or series shall be entitled to the receipt of
     dividends and amounts distributable upon liquidation, dissolution or
     winding-up in preference or priority to the holders of the Series F
     Preferred Shares ("SENIOR SHARES").

     8. VOTING.

     (a) If and whenever six (6) quaterly dividends (whether or not consecutive)
payable on

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the Series F Preferred Shares or any series or class of Parity Shares shall be
in arrears (which shall, with respect to any such quarterly dividend, mean that
any such dividend has not been paid in full), whether or not declared, the
number of Trustees then constituting the Board of Trustees shall be increased by
two (if not already increased by reason of similar types of provisions with
respect to Parity Shares of any other class or series which is entitled to
similar voting rights, other than the Series A Preferred Shares (the "VOTING
PARITY SHARES"); without limiting the foregoing, the Series B Preferred Shares,
the Series D Preferred Shares and the Series E Preferred Shares shall be deemed
to be entitled to voting rights similar to the Series F Preferred Shares) and
the holders of Series F Preferred Shares, together with the holders of all other
Voting Parity Shares then entitled to exercise similar voting rights, voting as
a single class regardless of series or class, shall be entitled to elect the two
additional Trustees to serve on the Board of Trustees at any annual meeting of
shareholders or at a special meeting of the holders of the Series F Preferred
Shares and the Voting Parity Shares called as hereinafter provided. At any time
when such right to elect Trustees separately shall have been so vested in the
holders of Series F Preferred Shares and the Voting Parity Shares, if
applicable, the Secretary of the Trust may, and upon the written request of the
holders of record of not less than 20% of the total number of Series F Preferred
Shares and Voting Parity Shares (addressed to the Secretary at the principal
office of the Trust) shall, call a special meeting of the holders of the Series
F Preferred Shares and of the Voting Parity Shares for the election of the two
Trustees to be elected by them as herein provided, such call to be made by
notice similar to that provided in the Bylaws of the Trust for a special meeting
of the shareholders or as required by law. Such special meeting shall be held,
in the case of such written request, within 90 days after the delivery of such
request, provided that the Trust shall not be required to call such a special
meeting if such request is received less than 120 days before the date fixed for
the next ensuing annual meeting of shareholders and the holders of the Series F
Preferred Shares and Voting Parity Share are offered the opportunity to elect
such Trustees at such annual meeting. The Trustees elected at any such special
meeting shall hold office until the next annual meeting of the shareholders or
special meeting held in lieu thereof if such office shall not have previously
terminated as provided herein. If any vacancy shall occur among the Trustees
elected by the holders of the Series F Preferred Shares and the Voting Parity
Shares by reason of death, resignation or disability, a successor shall be
elected by the Board of Trustees, upon the nomination of the then-remaining
Trustee elected by the holders of the Series F Preferred Shares and the Voting
Parity Shares or the successor of such remaining Trustee, to serve until the
next annual meeting of the shareholders or special meeting held in place thereof
if such office shall not have previously terminated as provided above. Whenever
all arrears in dividends on the Series F Preferred Shares and the Voting Parity
Shares then outstanding shall have been paid and dividends thereon for the
current Dividend Period shall have been declared and paid, or declared and set
apart for payment, then the right of the holders of the Series F Preferred
Shares and the Voting Parity Shares to elect such additional two Trustees shall
cease (but subject always to the same provision for the vesting of such voting
rights in the case of any similar future arrearages), and the terms of office of
all persons elected as Trustees by the holders of the Series F Preferred Shares
and the Voting Parity Shares shall forthwith terminate and the number of
Trustees constituting the Board of Trustees shall be reduced accordingly.

     (b) So long as any Series F Preferred Shares are outstanding, in addition
to any other vote or consent of shareholders required by law or by the
Declaration of Trust of the Trust, the affirmative vote or consent of at least
66-2/3% of the votes entitled to be cast by the holders of the outstanding

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Series F Preferred Shares voting as a single class with the holders of all other
classes or series of Voting Parity Shares entitled to vote on such matters,
given in person or by proxy, either in writing without a meeting or by vote at
any meeting called for the purpose, shall be necessary for effecting or
validating:

          (i) Any amendment, alteration or repeal of any of the provisions of,
     or the addition of any provision to, these Articles Supplementary, the
     Declaration of Trust or the By-Laws of the Trust that materially adversely
     affects the voting powers, rights or preferences of the holders of the
     Series F Preferred Shares; provided, however, that the amendment of or
     supplement to the provisions of the Declaration of Trust to authorize,
     create, increase or decrease the authorized amount of, or to issue Junior
     Shares, Series F Preferred Shares or any class of Parity Shares shall not
     be deemed to materially adversely affect the voting powers, rights or
     preferences of the holders of Series F Preferred Shares; or

          (ii) The authorization, creation of, increase in the authorized amount
     of, or issuance of shares of any class or series of Senior Shares or any
     security convertible or exchangeable into shares of any class or series of
     Senior Shares (whether or not such class or series of Senior Shares is
     currently authorized);

provided, however, that no such vote of the holders of Series F Preferred Shares
shall be required if, at or prior to the time when such amendment, alteration or
repeal is to take effect, or when the issuance of any such Senior Shares or
convertible or exchangeable security is to be made, as the case may be,
provision is made for the redemption of all outstanding Series F Preferred
Shares to the extent such redemption is authorized by Section 5 of this Article.

     For purposes of the foregoing provisions and all other voting rights under
these Articles Supplementary, each Series F Preferred Share shall have one (1)
vote per share, except that when any other class or series of preferred shares
of the Trust shall have the right to vote with the Series F Preferred Shares as
a single class on any matter, then the Series F Preferred Shares and such other
class or series shall have with respect to such matters one quarter of one vote
per $25.00 of stated liquidation preference. Except as otherwise required by
applicable law or as set forth herein or in the Declaration of Trust, the Series
F Preferred Shares shall not have any relative, participating, optional or other
special voting rights and powers other than as set forth herein, and the consent
of the holders thereof shall not be required for the taking of any action by the
Trust.

     (c) In no event shall the Series A Preferred Shares be treated as Parity
Shares for the purposes of this Section 8, and the voting rights of the Series A
Preferred Shares as fixed by the Articles Supplementary establishing such series
remain in full force and effect.

     9. RECORD HOLDERS.

     The Trust and the Transfer Agent may deem and treat the record holder of
any Series F Preferred Share as the true and lawful owner thereof for all
purposes, and neither the Trust nor the Transfer Agent shall be affected by any
notice to the contrary.

     10. RESTRICTIONS ON OWNERSHIP AND TRANSFER; REMEDIES.

     Article VII of the Declaration of Trust sets forth certain ownership and
transfer restrictions relating to the Equity Shares, including the Series F
Preferred Shares. Article VII of the Declaration

                                       10
<PAGE>

of Trust is hereby incorporated by reference herein.

     FOURTH: These Articles Supplementary have been duly adopted by all
necessary action on the part of the Trust.

     IN WITNESS WHEREOF, the Trust has caused these presents to be signed in its
name and on its behalf by its President and Chief Operating Officer and
witnessed by its Secretary, Vice President & General Counsel on September 13,
2001.

                                             CORPORATE OFFICE PROPERTIES TRUST

WITNESS:                                     By: /s/ Randall M. Griffin
                                                 -----------------------------
/s/ John H. Gurley                           Name:  Randall M. Griffin
----------------------------------           Title: President & Chief Operating
Name:  John H. Gurley                               Officer
Title: Secretary, Vice President &
       General Counsel

THE UNDERSIGNED, President and Chief Operating Officer of CORPORATE OFFICE
PROPERTIES TRUST, who executed on behalf of the Trust the Articles Supplementary
of which this Certificate is made a part, hereby acknowledges in the name and on
behalf of said Trust the foregoing Articles Supplementary to be the official act
of said Trust and hereby certifies that the matters and facts set forth herein
with respect to the authorization and approval thereof are true in all material
respects under the penalties of perjury.

/s/ Randall M. Griffin
--------------------------------------
Name:  Randall M. Griffin
Title: President & Chief Operating Officer

                                       11<PAGE>
                                                                     EXHIBIT 4.2

NUMBER                                                                    SHARES

  A REAL ESTATE INVESTMENT TRUST FORMED UNDER THE LAWS OF THE STATE OF MARYLAND

 SEE REVERSE FOR IMPORTANT NOTICE ON TRANSFER RESTRICTIONS AND OTHER INFORMATION

       THIS CERTIFICATE IS TRANSFERABLE IN MINNEAPOLIS, MN OR NEW YORK, NY

CUSIP  22002T405

                        CORPORATE OFFICE PROPERTIES TRUST

THIS CERTIFIES THAT

IS THE OWNER OF

FULLY PAID AND NONASSESSABLE SERIES F CUMULATIVE REDEEMABLE PREFERRED SHARES OF
BENEFICIAL INTEREST, LIQUIDATION PREFERENCE $25.00 PER SHARE OF Corporate Office
Properties Trust (the "Trust"), transferable on the books of the Trust by the
holder hereof in person or by its duly authorized attorney upon surrender of
this Certificate properly endorsed. This Certificate and the shares represented
hereby are issued and shall be held subject to all of the provisions of the
Declaration Of Trust And Bylaws of the Trust and any amendments thereto. This
Certificate is not valid unless countersigned and registered by the Transfer
Agent and Registrar.

In Witness Whereof, the Trust has caused this Certificate to be executed on its
behalf by its duly authorized officers.

DATED:

TREASURER/SECRETARY                                                    PRESIDENT

<PAGE>

                            [REVERSE OF CERTIFICATE]

                                IMPORTANT NOTICE

     The Trust will furnish to any shareholder, on request and without charge, a
full statement of the information required by Section 8-203(d) of the
Corporations and Associations Article of the Annotated Code of Maryland with
respect to the designations and any preferences, conversion and other rights,
voting powers, restrictions, limitations as to dividends and other
distributions, qualifications, and terms and conditions of redemption of the
shares of each class of beneficial interest which the Trust has authority to
issue and, if the Trust is authorized to issue any preferred or special class in
series, (i) the differences in the relative rights and preferences between the
shares of each series to the extent set, and (ii) the authority of the Board of
Trustees to set such rights and preferences of subsequent series. The foregoing
summary does not purport to be complete and is subject to and qualified in its
entirety by reference to the Declaration of Trust of the Trust, a copy of which
will be sent without charge to each shareholder who so requests. Such request
must be made to the Secretary of the Trust at its principal office or to the
Transfer Agent.

     The shares represented by this Certificate are subject to restrictions on
Beneficial Ownership, Constructive Ownership and Transfer for the purpose of the
Trust's maintenance of its status as a real estate investment trust (a "REIT")
under the Internal Revenue Code of 1986, as amended (the "Code"). Subject to
certain further restrictions and except as expressly provided in the Declaration
of Trust of the Trust, (i) no Person may Beneficially Own or Constructively Own
Common Shares of the Trust in excess of 9.8 percent (in value or number of
shares) of the outstanding Common Shares of the Trust unless such Person is an
Excepted Holder or a Permitted Holder (in which case the Excepted Holder Limit
shall be applicable); (ii) no Person may Beneficially Own or Constructively Own
Equity Shares of the Trust in excess of 9.8 percent of the value of the total
outstanding Equity Shares of the Trust, unless such Person is an Excepted Holder
or a Permitted Holder (in which case the Excepted Holder Limit shall be
applicable); (iii) no Person may Beneficially Own or Constructively Own Equity
Shares that would result in the Trust being "closely held" under Section 856(h)
of the Code or otherwise cause the Trust to fail to qualify as a REIT; and (iv)
no Person may Transfer Equity Shares if such Transfer would result in Equity
Shares of the Trust being owned by fewer than 100 Persons. Any Person who
Beneficially Owns or Constructively Owns or attempts to Beneficially Own or
Constructively Own Equity Shares which cause or will cause a Person to
Beneficially Own or Constructively Own Equity Shares in excess or in violation
of the above limitations must immediately notify the Trust. If any of the
restrictions on transfer or ownership are violated, the Equity Shares
represented hereby will be automatically transferred to a Trustee of a
Charitable Trust for the benefit of one or more Charitable Beneficiaries. In
addition, upon the occurrence of certain events, attempted Transfers in
violation of the restrictions described above may be void AB INITIO. All
capitalized terms in this legend have the meanings defined in the Declaration of
Trust of the Trust, as the same may be amended from time to time, a copy of
which, including the restrictions on transfer and ownership, will be furnished
to each holder of Equity Shares of the Trust on request and without charge. Such
request must be made to the Secretary of the Trust at its principal office or to
the Transfer Agent.

             KEEP THIS CERTIFICATE IN A SAFE PLACE. IF LOST, STOLEN
          OR DESTROYED, THE TRUST WILL REQUIRE A BOND OF INDEMNITY AS A
             CONDITION TO THE ISSUANCE OF A REPLACEMENT CERTIFICATE.

     The following abbreviations, when used in the inscription on the face of
this Certificate, shall be construed as if they were written out in full
according to applicable laws or regulations.

<TABLE>
<S>            <C>                        <C>             <C>                         <C>          <C>
TEN COM        -- as tenants in common    UNIF GIFT       ------- Custodian  ----     UNIF TRAN    ------- Custodian  ------
TEN ENT        -- as tenants by the       MIN ACT          (Cust)           (Minor)   MIN ACT      (Cust)             (Minor)
               entireties                                 Under Uniform Gifts to                   Under Uniform Transfers
JT TEN         -- as joint tenants with                   Minors Act of __________                 to Minors Act of _________
               right of survivorship                                      (Date)                                     (Date)
               and not as tenants in
               common

     FOR VALUE RECEIVED,                                         hereby sells, assigns and transfers unto
                         ---------------------------------------

  -------------------------------------------------------------------------------------------------------
                     (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE OF ASSIGNEE)

     _______________________(_________________) Series F Cumulative Redeemable Preferred Shares of beneficial interest of the Trust
represented by this Certificate and does not hereby irrevocably constitute and appoint ______________________________
___________ Attorney to transfer the said shares on the books of the Trust, with full power of substitution in the premises.

Dated:
         ------------------

                                                     --------------------------
                                                     NOTICE: THE SIGNATURE TO
                                                     THIS ASSIGNMENT MUST
                                                     CORRESPOND WITH THE NAME AS
                                                     WRITTEN UPON THE FACE OF
                                                     THIS CERTIFICATE IN EVERY
                                                     PARTICULAR, WITHOUT
                                                     ALTERATION OR ENLARGEMENT
                                                     OR ANY CHANGE WHATEVER.

</TABLE>

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