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                                                                     Exhibit 4.3

                                    FORM OF
                               EIGHTH AMENDMENT TO
                           SECOND AMENDED AND RESTATED
                        LIMITED PARTNERSHIP AGREEMENT OF
                        CORPORATE OFFICE PROPERTIES, L.P.


     THIS EIGHTH AMENDMENT (the "Amendment") to the Second Amended and Restated
Limited Partnership Agreement of Corporate Office Properties, L.P., a Delaware
limited partnership (the "Partnership"), is made and entered into as of
September 14, 2001, by and among the undersigned parties.

                                    RECITALS

     A.   The Partnership is a limited partnership organized under the
Delaware Revised Uniform Limited Partnership Act (the "Act") and governed by
that certain Second Amended and Restated Limited Partnership Agreement dated
as of January, 1999, as amended by that certain First Amendment to Second
Amended and Restated Limited Partnership Agreement dated as of December 21,
1999, that certain Second Amendment to Second Amended and Restated Limited
Partnership Agreement dated as of December 21, 1999, that certain Third
Amendment to Second Amended and Restated Limited Partnership Agreement dated
as of September 29, 2000, that certain Fourth Amendment to Second Amended and
Restated Limited Partnership Agreement dated as of November 27, 2000, that
certain Fifth Amendment to Second Amended and Restated Limited Partnership
Agreement dated as of January 25, 2001, that certain Sixth Amendment to
Second Amended and Restated Limited Partnership Agreement dated as of April
3, 2001, and that certain Seventh Amendment to Second Amended and Restated
Limited Partnership Agreement, dated as of August 30, 2001 (as amended, the
"Agreement").

     B.   The sole general partner of the Partnership is Corporate Office
Properties Trust, a real estate investment trust formed under the laws of the
State of Maryland (the "General Partner").

     C.   The General Partner has issued 1,425,000 Shares of its 9.875% Series F
Cumulative Redeemable Preferred Shares (the "Series F Preferred REIT Shares") in
a public offering (the "Offering").

     D.   As required under Sections 4.2(B) and (C) of the Agreement, the
General Partner intends to transfer the net proceeds of the Offering (or cause
them to be transferred) to or for the benefit of the Partnership in exchange for
additional Partnership Interests in the Partnership having designations, rights
and preferences substantially similar to the economic rights of the holders of
the Series F Preferred REIT Shares (the "Series F Preferred Units").

     E.   The General Partner desires to amend the Agreement to acknowledge the
contribution of the net proceeds of the Offering by the General Partner to the
Partnership in exchange for the Series F Preferred Units. Unless otherwise
defined herein, all


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capitalized terms used in this Amendment shall have the same meanings as set
forth in the Agreement.

     NOW THEREFORE, in consideration of the foregoing and of the mutual premises
set forth herein, the General Partner, intending to be legally bound hereby,
hereby amends the Agreement as follows, effective as of the date set forth
above.

     1.   The foregoing recitals to this Amendment are hereby incorporated in
and made a part of this Amendment.

          (a)  Upon consummation of the Offering, the General Partner shall
contribute the net proceeds of the Offering to the Partnership.

          (b)  Upon the contribution of the net proceeds of the Offering to the
Partnership by the General Partner, and in accordance with Section 4.2(B) of the
Agreement, the Partnership shall issue to the General Partner 1,425,000
Series F Preferred Units, equal to the number of Series F Preferred REIT Shares
issued by the General Partner in connection with the Offering.

          (c)  For purposes of the Agreement, including the maintenance of
Capital Accounts, the General Partner shall be treated as making a Capital
Contribution of $34,289,062.50, equal to the product of $24.0625 times
the number of Series F Preferred Units issued to the General Partner.

          (d)  The General Partner is hereby amending Exhibit 1 to the Agreement
by substituting for the existing addendum to EXHIBIT 1 the Addendum to EXHIBIT 1
in the form attached hereto to reflect the issuance of the Series F Preferred
Units to the General Partner.

     2.   Except as explicitly modified by this Amendment, all of the provisions
of the Agreement are hereby ratified and confirmed, and shall remain in full
force and effect.

     3.   This Amendment shall take effect upon the contribution of the net
proceeds of the Offering to the Partnership by the General Partner, and in the
event such contribution is not made, this Amendment shall be of no force or
effect.


                            (SIGNATURE PAGE FOLLOWS)


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     In witness whereof, the General Partner has executed this Amendment as of
the day and year first above written.


                                        CORPORATE OFFICE PROPERTIES TRUST,
                                        a Maryland Real Estate Investment Trust

                                        By:
                                            -----------------------------------
                                        Name:  Roger A. Waesche, Jr.
                                        Title: Senior Vice President and
                                               Chief Financial Officer


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                                    EXHIBIT 1

                                    ADDENDUM

<Table>
<Caption>

                                                   Liquidation
                                                   Preference
   Series                              No. of          Per         Priority                                    Conversion
  Preferred     Preferred Limited     Preferred     Preferred     Percentage                   Conversion     Commencement
    Units            Partner            Units         Unit         Return *       Priority       Factor           Date
  ---------     -----------------     ---------    -----------    ----------      --------     -----------    ------------
  <S>           <C>                   <C>          <C>            <C>             <C>          <C>            <C>
      A          General Partner              1        $25           1.375%        Senior        1.8748         8/28/2000
      B          General Partner      1,250,000        $25            2.50%        Senior         None             N/A
      C                UPG            1,016,662        $25             **          Senior        2.381         12/22/2000
      D          General Partner        544,000        $25            1.00%        Senior         ***              ***
      E          General Partner      1,150,000        $25          2.5625%        Senior         None             N/A
      F          General Partner      1,425,000        $25                         Senior         None             N/A
</Table>
----------

     *    Priority Return Percentage is expressed as a percentage of the
Liquidation Preference per Distribution Period. SEE the Agreement for the
definitions of "Priority Return Percentage," "Liquidation Preference" and
"Distribution Period."

     **   Priority Percentage Return for the Series C Preferred Units shall be:

          2.25% from December 21, 1999 to December 20, 2009;
          2.625% from December 21, 2009 to December 20, 2014; and
          3.00% thereafter.

          The Distribution Period for the Series C Preferred Units shall be each
calendar quarter ending March 31, June 30, September 30 and December 31 of each
year.

     ***  With respect to any series of Preferred Units issued to the General
Partner pursuant to Section 4.2(B) of the Agreement, the Conversion Commencement
Date and the applicable Conversion Factor shall correspond to the conversion
commencement date and conversion factor of the related issuance of securities by
the General Partner as provided in Section 4.2(B) of the Agreement. SEE Section
9.8(A)(1) of the Agreement.