8-K

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, DC  20549

FORM 8-K

CURRENT REPORT
Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of report (Date of earliest event reported) April 12, 2007 (April 6, 2007)

CORPORATE OFFICE PROPERTIES TRUST
(Exact name of registrant as specified in its charter)

Maryland	1-14023	23-2947217
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification Number)

6711 Columbia Gateway Drive, Suite 300
Columbia, Maryland 21046

(Address of principal executive offices)

(443) 285-5400

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2 below):

o Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 1.01               Entry into a Material Definitive Agreement.

On April 6, 2007, Corporate Office Properties Trust (the “Registrant”), the General Partner of Corporate Office Properties, L.P. (the “Operating Partnership”), entered into the Twenty-Third Amendment (the “Amendment”) to the Second Amended and Restated Limited Partnership Agreement (as so amended, the “Partnership Agreement”) of Corporate Office Properties, L.P.  The Amendment, which is attached hereto as Exhibit 10.1, was entered into in connection with the issuance by the Operating Partnership of an aggregate of 262,165 common units in the Operating Partnership valued at $12.5 million to an unrelated entity effective April 6, 2007 in connection with the acquisition of property by a wholly owned subsidiary of the Registrant.  Other than to reflect the admission of such entity into the Operating Partnership, the Amendment contains no substantive terms.

Item 9.01               Financial Statements and Exhibits

(a)           Financial Statements of Businesses Acquired

None

(b)           Pro Forma Financial Information

None

(c)           Shell Company Transactions

None

(d)           Exhibits

Exhibit Number	Exhibit Title
10.1	Twenty-Third Amendment to Second Amended and Restated Limited Partnership Agreement of Corporate Office Properties, L.P., dated April 6, 2007.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date:  April 12, 2007

CORPORATE OFFICE PROPERTIES TRUST
By:	/s/ RANDALL M. GRIFFIN
Name:	Randall M. Griffin
Title:	President and Chief Executive Officer

EXHIBIT INDEX

Exhibit Number	Exhibit Title
10.1	Twenty-Third Amendment to Second Amended and Restated Limited Partnership Agreement of Corporate Office Properties, L.P., dated April 6, 2007.

EX-10.1

Exhibit 10.1

TWENTY-THIRD AMENDMENT
TO
SECOND AMENDED AND RESTATED
LIMITED PARTNERSHIP AGREEMENT
OF
CORPORATE OFFICE PROPERTIES, L.P.

This Twenty-Third 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 April 6, 2007, by the undersigned.

Recitals

A.            The Partnership is a limited partnership organized under the Delaware Revised Uniform Limited Partnership Act and governed by that certain Second Amended and Restated Limited Partnership Agreement dated as of December 7, 1999, as amended to the date hereof (as amended, the “Partnership 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.            Pursuant to Section 11.1 (b) (iii), the General Partner desires to amend the Partnership Agreement to reflect the admission, substitution, termination and/or withdrawal of various limited partners in accordance with the terms of the Partnership Agreement.

NOW THEREFORE, the General Partner, intending to be legally bound, hereby amends the Partnership Agreement as follows, effective as of the date first set forth above.

1.Exhibit 1, Schedule of Partners, as attached hereto and by this reference made a part hereof, is hereby substituted for and intended to replace any prior Exhibit 1 attached to a prior Amendment to the Partnership Agreement, and as attached hereto shall be a full and complete listing of all the general and limited partners of the Partnership as of the date of this Amendment, same being intended and hereby superceding all prior Exhibit 1 listings.

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:	/s/ RANDALL M. GRIFFIN
	Randall M. Griffin
	President and Chief Executive Officer

Exhibit 1 Addendum

Schedule of Partners

General Partner	Common Units of  Partnership  Units	Series G Preferred  Units	Series H Preferred Units	Series I Preferred Units	Series J Preferred Units	Series K Preferred Units
Corporate Office Properties Trust	44,938,069	2,200,000	2,000,000		3,390,000	531,667
Limited Partners and Preferred Limited Partners
Jay H. Shidler	452,878
Shidler Equities, L.P.	2,995,439
Clay W. Hamlin, III	489,917
LBCW Limited Partnership	2,681,107
Robert L. Denton	400,000
James K. Davis	51,589
John E. De B. Blockey, Trustee of the John E. de B. Blockey Living Trust dated 9/12/88	300,625
Frederick K. Ito Trust	20,340
June Y. I. Ito Trust	20,335
RP Investments, LLC	100,000
Denise J. Liszewski	23,333
Samuel Tang	4,389
Lawrence J. Taff	13,733
Kimberly F. Aquino	2,937
M.O.R. XXIX Associates Limited Partnership	148,381
M.O.R. 44 Gateway Associates Limited Partnership	1
John Parsinen	49,434
M.O.R. Commons Limited Partnership	7
John Edward De Burgh Blockey and Sanda Juanita Blockey	10,476
Lynn Hamlin	121,411
Housing Affiliates, Inc.	4,402
Reingle Corp.	730
Joseph Tawil	2,160
The Lovejoy Trust	59,528
The Century Trust	59,528
A. Charles Wilson & Betty S. Wilson Trust	5,908
Harold & Renee Holland	4,320
Irwin Hoffman	1,880
Rouse 1988 Trust	2,160
CB Management, L.L.C.	2,497
Patriot Partner, L.L.C.	25,000
National Prostate Cancer Coalition	400
John A. Luetkemeyer, Jr.	38,954
Lawrence G. Rief	2,526
Arthur Ashe Youth Tennis & Education	300
Heritage Foundation	200
Volunteers in Medicine	500
David D. Jenkins	262,165
TRC Associates Limited Partnership				352,000
	53,297,559	2,200,000	2,000,000	352,000	3,390,000	531,667