UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Amendment No. 4 to
SCHEDULE TO

Tender Offer Statement Pursuant to Section 14(d)(1) or 13(e)(1)
of the Securities Exchange Act of 1934

PIEDMONT OFFICE REALTY TRUST, INC.

(Name of Subject Company)

Series C (PDM B-3) of Tender Investors, LLC,
which is managed by
Tender Investors Manager LLC,
whose sole member is
Apex Real Estate Advisors, LLC

(Name of Filing Persons - Offerors)

SHARES OF CLASS B-3 COMMON STOCK, PAR VALUE $0.01

(Title of Class of Securities)

720190 503

(CUSIP Number of Class of Securities)

Brent Donaldson
Series C (PDM B-3) of Tender Investors, LLC,
a Delaware series limited liability company
c/o Tender Investors Manager, LLC
6114 La Salle Ave., #345
Oakland, CA 94611
Tel: 510.619.3636
Fax: 925.403.7967

(Name, Address, and Telephone Number of Person Authorized to Receive Notices
and Communications on Behalf of Filing Persons)

*For purposes of calculating the original filing fee only. In the original filing, the offer was to purchase of 2,100,000 Shares at a purchase price equal to $14.00 per Share in cash.

ý    Check box if any part of the fee is offset as provided by Rule 0-11(a)(2) and identify the filing with which the offsetting fee was previously paid. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

Amount Previously Paid:       $5,880

Form or Registration:              Schedule TO-T

Number:                                       005-80150

Filing Party:                              Series C (PDM B-3) of Tender Investors, LLC

Date Filed:                                August 3, 2010

¨    Check the box if the filing relates solely to preliminary communications made before the commencement of a tender offer.

Check the appropriate boxes below to designate any transactions to which the statement relates:

ý    third party tender offer subject to Rule 14d-1.

¨    issuer tender offer subject to Rule 13e-4.

¨    going private transaction subject to Rule 13e-3.

¨    amendment to Schedule 13D under Rule 13d-2.

Check the following box if the filing is a final amendment reporting the results of the tender offer: ¨

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TENDER OFFER

This Amendment No. 4 to the Schedule TO originally filed on August 3, 2010 (the “Original Schedule TO”) by Series C (PDM B-3) of Tender Investors, LLC, a Delaware series limited liability company (the “Purchaser”), as amended by Amendment Nos. 1, 2 and 3 thereto, relates to the amended offer to purchase up to 427,000 shares of Class B-3 common stock (the “Shares”) of Piedmont Office Realty Trust, Inc., the subject company (the “Amended Offer”), is being filed to announce that 556 Shares had been tendered as of October 18, 2010, the date on which the Expiration Date of the Amended Offer was extended to November 15, 2010. 

Items 1 through 11.

The information in the Amended and Restated Offer to Purchase dated August 26, 2010, including all schedules thereto, previously filed as Exhibit (a)(1) to Amendment No. 1, is hereby expressly incorporated herein by reference in response to Items 1 through 11 of this Statement, except as set forth above or below.

Item 12.  Exhibits.

(a)(1) Amended and Restated Offer to Purchase dated August 26, 2010**

(a)(2) Assignment Form*

(a)(3) Amended and Restated Form of Letter to Shareholders dated August 26, 2010**

(a)(4) Form of Advertisement in Investor’s Business Daily*

(a)(5) Press Release of Series C (PDM B-3) of Tender Investors, LLC, dated August 26, 2010**

(a)(6) Form of Amended and Restated Advertisement in Investor’s Business Daily***

(a)(7) Press Release of Series C (PDM B-3) of Tender Investors, LLC, dated October 18, 2010****

(a)(8) Press Release of Series C (PDM B-3) of Tender Investors, LLC, dated October 20, 2010

(b)-(h) Not applicable  

* Previously filed with Original Schedule TO. 

** Previously filed with Amendment No. 1 to Original Schedule TO.

*** Previously filed with Amendment No. 2 to Original Schedule TO.

**** Previously filed with Amendment No. 3 to Original Schedule TO.

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SIGNATURES

After due inquiry and to the best of its knowledge and belief, the undersigned certify that the information set forth in this statement is true, complete and correct.

Dated:  October 20, 2010

SERIES C (PDM B-3) OF TENDER INVESTORS, LLC,

A DELAWARE SERIES LIMITED LIABILITY COMPANY

By: Tender Investors Manager, LLC

Its:  Manager

By:     Apex Real Estate Advisors, LLC

Its:      Manager

/s/Brent R. Donaldson                                             

By:     Brent Donaldson

Its:      Managing Principal

TENDER INVESTORS MANAGER, LLC,

A DELAWARE LIMITED LIABILITY COMPANY

By: Apex Real Estate Advisors, LLC

Its:  Manager

/s/Brent R. Donaldson                                                        

By: Brent Donaldson

Its:      Managing Principal

APEX REAL ESTATE ADVISORS, LLC,

A DELAWARE LIMITED LIABILITY COMPANY

/s/ Brent R. Donaldson                                                              

By: Brent Donaldson

Its:  Managing Principal

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EXHIBIT INDEX

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Exhibit (a)(8)

PRESS RELEASE FOR IMMEDIATE RELEASE

As previously announced, Series C (PDM B-3) of Tender Investors, LLC amended its tender offer for Class B-3 Shares of Piedmont Office Realty Trust, Inc. (NYSE:PDM) increasing the price to $15.05 per share and extending the Expiration Date to November 15, 2010.

Point Richmond, Calif. (Business Wire)—October 20, 2010—Series C (PDM B-3) of Tender Investors, LLC (“Purchaser”) announced on October 18, 2010, an amendment to its tender offer for 427,000 Class B-3 Shares (the “Shares”) of Piedmont Office Realty Trust, Inc. (NYSE:PDM).  The Purchaser amended its offer to increase the price to $15.05 per share and to extend the Expiration Date for the offer to November 15, 2010.    As of October 18, 2010, 556 shares had been tendered to the Purchaser.

The Purchaser has filed with the U.S. Securities and Exchange Commission an amendment to its Schedule TO providing details of its amended offer.  The Purchaser has previously filed an Amended and Restated Offer to Purchase and related materials with the U.S. Securities and Exchange Commission detailing the terms of its offer.  Other than the price and extension of the Expiration Date announced above (including the extension of the right to withdraw Shares tendered through such date), all other terms of the offer remain unchanged.  Shareholders should read the Amended Schedule TO and the related materials carefully because they contain important information.

Shareholders may obtain a free copy of the Amended Schedule TO and other documents by calling the Purchaser at (510) 619-3637, or by making a written request addressed to the Purchaser either at 6114 La Salle Ave. #345, Oakland, CA  94611 or by email to offers@tendermanagerllc.com.  Shareholders may also visit the Purchaser’s website at www.tendermanagerllc.com (click on Piedmont Office Realty Trust Tender Offer Document) or visiting the U.S. Securities and Exchange Commission’s website at www.sec.gov.  Shareholders also may obtain a copy of these documents, without charge, from our website at www.tendermanagerllc.com (click on Tender Offer Information) or by calling (510) 619-3637.

Contact:

Arnold Brown

Tender Investors Manager, LLC

(510) 619-3637

offers@tendermanagerllc.com