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

Exhibit 10.1

TWENTY-SEVENTH AMENDMENT

TO

SECOND AMENDED AND RESTATED

LIMITED PARTNERSHIP AGREEMENT

OF

CORPORATE OFFICE PROPERTIES, L.P.

This Twenty-Seventh 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 February 3, 2011, 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/ Xxxxx X. Xxxxxxx, Xx.
		Xxxxx X. Xxxxxxx, Xx.
		President

Exhibit 1 Addendum—27th Amendment

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		64,610,967		2,200,000		2,000,000				3,390,000		531,667
Limited Partners and Preferred Limited Partners
Xxx X. Xxxxxxx		452,878
Xxxxxxx Equities, L.P.		1,395,439
Xxxx X. Xxxxxx, III		91,592
LBCW Limited Partnership		1,331,107
Xxxxxx X. Xxxxxx		348,000
Xxxxx X. Xxxxx		51,589
RP Investments, LLC		10,000
Xxxxxx X. Xxxxxxxxx		4,433
Xxxxxx Xxxx		4,389
Xxxxxxxx X. Xxxx		13,733
Xxxxxxxx X. Xxxxxx		2,937
M.O.R. 44 Gateway Associates Limited Partnership		1
Xxxx Xxxxxxxx		49,434
M.O.R. Commons Limited Partnership		7
Xxxx Xxxxxx		121,411
Housing Affiliates, Inc.		4,402
Reingle Corp.		730
Xxxxxx Xxxxx		2,160
The Xxxxxxx Trust		59,528
The Century Trust		59,528
A. Xxxxxxx Xxxxxx & Xxxxx X. Xxxxxx Trust		5,908
Xxxxxx & Xxxxx Xxxxxxx		4,320
Xxxxx Xxxxxxx		1,880
The Xxxxx Family Exemption Trust		2,160
Xxxxxxxx X. Xxxx		2,526
Xxxxx X. Xxxxxxx		262,165
RA & DM, Inc.		2,954
Xxxxxxx Xxxxx		43,817
Xxxxxx Xxxxxxx		23,336
Xxxxxxx Xxxxxxxx		14,019
Xxxxxxx Xxxxxxx		8,988
Xxxxxx Xxxxxxx		8,988
Xxxxxxx Xxxxxxx		3,899
Xxxxxxxx Xxxxxxx		880
Xxxxxx Xxxxxx		5,427
Xxxx Xxxxx		880
Xxxxx XxXxxxx		2,513
Xxxxx Deutsch		22
Xxxxx Xxxxx		22
TRC Associates Limited Partnership								352,000
		69,008,969		2,200,000		2,000,000		352,000		3,390,000		531,667