8-K

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 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): September 11, 2007

OTTER TAIL CORPORATION

(Exact name of registrant as specified in its charter)

Minnesota (State or other jurisdiction of incorporation)	0-00368 (Commission File Number)	41-0462685 (I.R.S. Employer Identification No.)
215 South Cascade Street, P.O. Box 496, Fergus Falls, MN		56538-0496
(Address of principal executive offices)		(Zip Code)

Registrant’s telephone number, including area code: (866) 410-8780

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:

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))

TABLE OF CONTENTS

	Item 1.01 Entry into a Material Definitive Agreement
	Item 9.01 Financial Statements and Exhibits
Signature
Exhibit Index
Amendment No. 5 to Participation Agreement

Item 1.01 Entry into a Material Definitive Agreement

On September 11, 2007, Otter Tail Corporation dba Otter Tail Power Company, Central Minnesota Municipal Power Agency, Great River Energy, Heartland Consumers Power District, Montana-Dakota Utilities Co., a division of MDU Resources Group, Inc., Southern Minnesota Municipal Power Agency and Western Minnesota Municipal Power Agency (collectively, the “Owners”) entered into Amendment No. 5 to Participation Agreement, dated as of September 1, 2007 (“Amendment No. 5”). Amendment No. 5 amends the Participation Agreement, dated as of June 30, 2005 (the “Agreement”), which was previously amended by Amendment No. 1 to the Participation Agreement, dated as of June 1, 2006 (“Amendment No. 1”), Amendment No. 2 to the Participation Agreement, dated as of August 18, 2006 (“Amendment No. 2”), Amendment No. 3 to Participation Agreement, dated as of September 1, 2006 (“Amendment No. 3”) and Amendment No. 4 to Participation Agreement, dated as of June 8, 2007 (“Amendment No. 4”) (the Agreement, as so amended by Amendment No. 1, Amendment No. 2, Amendment No. 3, Amendment No. 4, and Amendment No. 5, the “Amended Agreement”). The Amended Agreement, which relates to the planned construction of a new 630 megawatt coal fueled, base-load electric generation plant (the “Big Stone II Plant”) adjacent to the existing 450 megawatt electric generation plant near Big Stone, South Dakota, is an agreement to jointly develop, finance, construct, own (as tenants in common) and manage the Big Stone II Plant and includes provisions which obligate the parties to the agreement to obtain financing and pay their share of development, construction, operating and maintenance costs for the Big Stone II Plant. The Amended Agreement establishes a Coordinating Committee and an Engineering and Operating Committee to manage the development, design, construction, operation and maintenance of the Big Stone II Plant.

Amendment No. 5 extends the date on which the Owners, through the Coordinating Committee, must meet to vote on whether to continue the project from a date agreed upon by all of the Owners that shall be not later than September 12, 2007 to a date agreed upon by all of the Owners that shall be on September 21, 2007.

Item 9.01 Financial Statements and Exhibits

      (d) Exhibits

10.1 Amendment No. 5 to Participation Agreement, dated as of September 1, 2007, by and among Central Minnesota Municipal Power Agency, Great River Energy, Heartland Consumers Power District, Montana-Dakota Utilities Co., a division of MDU Resources Group, Inc., Otter Tail Corporation dba Otter Tail Power Company, Southern Minnesota Municipal Power Agency and Western Minnesota Municipal Power Agency, as Owners, amending the Participation Agreement, dated as of June 30, 2005, by and among the Owners

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Signature

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, thereunto duly authorized.

	OTTER TAIL CORPORATION
Date: September 12, 2007	By /s/ Kevin G. Moug
	Kevin G. Moug
	Chief Financial Officer and Treasurer

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Exhibit Index

10.1 Amendment No. 5 to Participation Agreement, dated as of September 1, 2007, by and among Central Minnesota Municipal Power Agency, Great River Energy, Heartland Consumers Power District, Montana-Dakota Utilities Co., a division of MDU Resources Group, Inc., Otter Tail Corporation dba Otter Tail Power Company, Southern Minnesota Municipal Power Agency and Western Minnesota Municipal Power Agency, as Owners, amending the Participation Agreement, dated as of June 30, 2005, by and among the Owners

EX-10.1

EXHIBIT 10.1

Big Stone II Power Plant

Amendment No. 5 to
Participation Agreement

By and Among

CENTRAL MINNESOTA MUNICIPAL POWER AGENCY,

GREAT RIVER ENERGY,

HEARTLAND CONSUMERS POWER DISTRICT,

MONTANA-DAKOTA UTILITIES CO., A DIVISION OF MDU

RESOURCES GROUP, INC.,

OTTER TAIL CORPORATION dba OTTER TAIL POWER COMPANY,

SOUTHERN MINNESOTA MUNICIPAL POWER AGENCY, AND

WESTERN MINNESOTA MUNICIPAL POWER AGENCY

As
Owners

Effective

September 1, 2007

Amendment No. 5 to Participation Agreement
Effective: September 1, 2007
Vote Date: On September 21, 2007

1

Amendment No. 5 to Participation Agreement

     THIS AMENDMENT NO. 5 TO PARTICIPATION AGREEMENT (this “Amendment”) is made as of September 1, 2007, by and among Central Minnesota Municipal Power Agency, an agency incorporated under the laws of the State of Minnesota (“CMMPA”), Great River Energy, a cooperative corporation incorporated under the laws of the State of Minnesota (“GRE”), Heartland Consumers Power District, a consumers power district formed and organized under the South Dakota Consumers Power District Law (Chapter 49-35 of the South Dakota Codified Laws) (“Heartland”), Montana-Dakota Utilities Co., a Division of MDU Resources Group, Inc., a corporation incorporated under the laws of the State of Delaware (“Montana-Dakota”), Otter Tail Corporation, a corporation incorporated under the laws of the State of Minnesota, doing business as Otter Tail Power Company (“Otter Tail”), Southern Minnesota Municipal Power Agency, a municipal corporation and political subdivision of the State of Minnesota (“SMMPA”), and Western Minnesota Municipal Power Agency, a municipal corporation and political subdivision of the State of Minnesota (“WMMPA”) (each individually a “Party” and, collectively, the “Parties”).

RECITALS

     WHEREAS, the Parties have entered into a Participation Agreement, dated June 30, 2005 (the “Agreement”), and an Amendment No. 1 to the Participation Agreement dated effective as of June 1, 2006 (the “Amendment No. 1”), an Amendment No. 2 to the Participation Agreement dated August 1, 2006 (the “Amendment No. 2”), Amendment No. 3 to the Participation Agreement dated effective as of September 1, 2006 (the “Amendment No. 3”), and an Amendment No. 4 to the Participation Agreement dated effective June 8, 2007 (individually, the “Amendment No. 4” and collectively with the Agreement and the Amendment No. 1, the Amendment No. 2, and the Amendment No. 3, the “Amended Agreement”), to provide for their ownership as tenants in common of BSP II and set forth certain responsibilities and mechanisms for the design, construction, ownership, operation, maintenance and repair of BSP II; and

     WHEREAS, the Parties desire to amend the Amended Agreement as and to the extent provided in this Amendment.

     NOW, THEREFORE, in consideration of the agreements and covenants set forth herein, and other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, and intending to be legally bound by this Amendment, the Parties covenant and agree as follows:

AGREEMENTS

     1.01 Defined Terms. Capitalized terms used but not otherwise defined herein shall have the meanings ascribed to such terms in the Agreement.

Amendment No. 5 to Participation Agreement
Effective: September 1, 2007
Vote Date: On September 21, 2007

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     1.02 Amendments. The Amended Agreement is hereby amended as follows:

     (a) In Section 3.05(b) of the Amended Agreement, the words “not later than September 12, 2007” are hereby deleted and replaced with “on September 21, 2007”.

     1.03 Continuing Effect; Ratification. Except as expressly amended herein, all other terms, covenants and conditions contained in the Amended Agreement shall continue to remain unchanged and in full force and effect and are hereby ratified and confirmed.

      1.04 Governing Law. This Amendment shall be interpreted and enforced in accordance with the Laws of the State of South Dakota, notwithstanding any conflict of law provision to the contrary.

     1.05 Captions. All titles, subject headings, section titles and similar items are provided for the purpose of reference and convenience and are not intended to affect the meaning of the content or scope of this Amendment.

     1.06 Counterparts. This Amendment may be executed in any number of counterparts, each of which shall be deemed to be an original and all of which together shall constitute but one and the same agreement. Counterpart signatures may be delivered by facsimile or electronic transmission, each of which shall have the same force and effect as an original signed copy.

     1.07 Authority. Each signatory to this Amendment represents that he/she has the authority to execute and deliver this Amendment on behalf of the party set forth above his/her signature.

[Signature pages follow.
The remainder of this page is intentionally blank.]

Amendment No. 5 to Participation Agreement
Effective: September 1, 2007
Vote Date: On September 21, 2007

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     IN WITNESS WHEREOF, the Parties have caused their names to be hereunto subscribed by their officers thereunto duly authorized, intending thereby that this Amendment shall be effective as of the date set forth above.

OWNERS:

CENTRAL MINNESOTA MUNICIPAL
POWER AGENCY

By /s/ Bob Elston
Name:	Bob Elston
Title:	President

[Signatures continued on next page.]

Amendment No. 5 to Participation Agreement
Effective: September 1, 2007
Vote Date: On September 21, 2007

4

     IN WITNESS WHEREOF, the Parties have caused their names to be hereunto subscribed by their officers thereunto duly authorized, intending thereby that this Amendment shall be effective as of the date set forth above.

OWNERS:

HEARTLAND CONSUMERS POWER
DISTRICT

By /s/ Mike McDowell
Name:	Mike McDowell
Title:	General Manager

[Signatures continued on next page.]

Amendment No. 5 to Participation Agreement
Effective: September 1, 2007
Vote Date: On September 21, 2007

5

     IN WITNESS WHEREOF, the Parties have caused their names to be hereunto subscribed by their officers thereunto duly authorized, intending thereby that this Amendment shall be effective as of the date set forth above.

OWNERS:

SOUTHERN MINNESOTA MUNICIPAL
POWER AGENCY

By /s/ Raymond A. Hayward
Name:	Raymond A. Hayward
Title:	Executive Director & CEO

[Signatures continued on next page.]

Amendment No. 5 to Participation Agreement
Effective: September 1, 2007
Vote Date: On September 21, 2007

6

     IN WITNESS WHEREOF, the Parties have caused their names to be hereunto subscribed by their officers thereunto duly authorized, intending thereby that this Amendment shall be effective as of the date set forth above.

OWNERS:

WESTERN MINNESOTA MUNICIPAL
POWER AGENCY

By /s/ Thomas J. Heller
Name:	Thomas J. Heller
Title:	Asst. Secretary & Asst. Treasurer

[Signatures continued on next page.]

Amendment No. 5 to Participation Agreement
Effective: September 1, 2007
Vote Date: On September 21, 2007

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     IN WITNESS WHEREOF, the Parties have caused their names to be hereunto subscribed by their officers thereunto duly authorized, intending thereby that this Amendment shall be effective as of the date set forth above.

OWNERS:

GREAT RIVER ENERGY

By /s/ David Saggau
Name:	David Saggau
Title:	President & CEO

[Signatures continued on next page.]

Amendment No. 5 to Participation Agreement
Effective: September 1, 2007
Vote Date: On September 21, 2007

8

     IN WITNESS WHEREOF, the Parties have caused their names to be hereunto subscribed by their officers thereunto duly authorized, intending thereby that this Amendment shall be effective as of the date set forth above.

OWNERS:

MONTANA-DAKOTA UTILITIES CO.,
a Division of MDU Resources Group, Inc.

By /s/ Bruce Imsdahl
Name:	Bruce Imsdahl
Title:	President & CEO

[Signatures continued on next page.]

Amendment No. 5 to Participation Agreement
Effective: September 1, 2007
Vote Date: On September 21, 2007

9

     IN WITNESS WHEREOF, the Parties have caused their names to be hereunto subscribed by their officers thereunto duly authorized, intending thereby that this Amendment shall be effective as of the date set forth above.

OWNERS:

OTTER TAIL CORPORATION
dba Otter Tail Power Company

By /s/ Chuck MacFarlane
Name:	Chuck MacFarlane
Title:	President

Amendment No. 5 to Participation Agreement
Effective: September 1, 2007
Vote Date: On September 21, 2007

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