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Exhibit 4.1 FOURTH AMENDMENT TO CREDIT AGREEMENT THIS FOURTH AMENDMENT, dated as of April 28, 2004, amends and modifies a
certain Credit Agreement, dated as of April 30, 2002, as amended by amendments
dated as of September 19, 2002, April 29, 2003 and August 25, 2003 (as so
amended, the Credit Agreement), among OTTER TAIL CORPORATION, a Minnesota
corporation (the Borrower), U.S. BANK NATIONAL ASSOCIATION, as Agent (in such
capacity, the Agent), and the Banks, as defined therein. Terms not otherwise
expressly defined herein shall have the meanings set forth in the Credit
Agreement. FOR VALUE RECEIVED, the Borrower, the Agent and the Banks agree that the
Credit Agreement is amended as follows. ARTICLE I  AMENDMENT TO THE CREDIT AGREEMENT 1.1 Termination Date. The definition of Termination Date in Section
1.1 is amended by deleting April 28, 2004 (added by the Second Amendment) and
inserting April 27, 2005 in place thereof. 1.2 Construction. All references in the Credit Agreement to this
Agreement, herein and similar references shall be deemed to refer to the
Credit Agreement as amended by this Amendment. ARTICLE II  REPRESENTATIONS AND WARRANTIES To induce the Agent and the Banks to enter into this Amendment and to make
and maintain the Loans under the Credit Agreement as amended hereby, the
Borrower hereby warrants and represents to the Agent and the Banks that it is
duly authorized to execute and deliver this Amendment, and to perform its
obligations under the Credit Agreement as amended hereby, and that this
Amendment constitutes the legal, valid and binding agreement of the Borrower,
enforceable in accordance with its terms. ARTICLE III  CONDITIONS PRECEDENT This Amendment shall become effective on the date first set forth above,
provided, however, that the effectiveness of this Amendment is subject to the
satisfaction of each of the following conditions precedent: 3.1 Warranties. Before and after giving effect to this Amendment, the
representations and warranties in Article VII of the Credit Agreement shall be
true and correct as though made on the date hereof, except for changes that are
permitted by the terms of the Credit Agreement. The execution by the Borrower
of this Amendment shall be deemed a representation that the Borrower has
complied with the foregoing condition.




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3.2 Defaults. Before and after giving effect to this Amendment, no
Default and no Event of Default shall have occurred and be continuing under the
Credit Agreement. The execution by the Borrower of this Amendment shall be
deemed a representation that the Borrower has complied with the foregoing
condition. 3.3 Documents and Fee. The following shall have been executed, delivered
and paid to the Agent: (a) This Amendment, executed by the Borrower, the Agent and the Banks;(b) The Acknowledgment in the form attached hereto, executed by the
Guarantor;(c) A supplement to the Agents Fee Letter (which, together with the
original Agents Fee Letter and the prior supplement dated as of August
20, 2003, will be deemed the Agents Fee Letter for purposes of
reference thereto in the Credit Agreement); and(d) A non-refundable fee of $35,000 in consideration of the extension of
the Commitments hereunder, which fee shall be divided and paid by the
Agent to the Banks in proportion to their respective Percentages.
 ARTICLE IV  GENERAL 4.1 Expenses. The Borrower agrees to reimburse the Agent upon demand for
all reasonable expenses (including reasonable attorneys fees and legal
expenses) incurred by this Agent in the preparation, negotiation and execution
of this Amendment and any other document required to be furnished herewith. 4.2 Counterparts. This Amendment may be executed in as many counterparts
as may be deemed necessary or convenient, and by the different parties hereto
on separate counterparts, each of which, when so executed, shall be deemed an
original but all such counterparts shall constitute but one and the same
instrument. 4.3 Severability. Any provision of this Amendment which is prohibited or
unenforceable in any jurisdiction shall, as to such jurisdiction, be
ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining portions hereof or affecting the validity or
enforceability of such provisions in any other jurisdiction. 4.4 Law. This Amendment shall be a contract made under the laws of the
State of Minnesota, which laws shall govern all the rights and duties
hereunder. 4.5 Successors; Enforceability. This Amendment shall be binding upon the
Borrower, and Agent and the Banks and their respective successors and assigns,
and shall inure to the benefit of the Borrower, the Agent and the Banks and the
successors and assigns of the Agent and the Banks. 2




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Except as hereby amended, the Credit Agreement shall remain in full force and
effect and is hereby ratified and confirmed in all respects. IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed at Minneapolis, Minnesota by their respective officers thereunto duly
authorized as of the date first written above. OTTER TAIL CORPORATIONBy:
    /s/ Kevin G. MougTitle:
    CFOU.S. BANK NATIONAL ASSOCIATION,
     as Agent and a BankBy:
    /s/ Randy SalzwedelRandy A. SalzwedelVice PresidentBANK ONE, N.A., as a BankBy:
    /s/ Sharon K. WebbSharon K. WebbDirectorBANK HAPOALIM B.M., as a BankBy:
    /s/ Laura A. RaffaTitle:
    Executive Vice PresidentandBy:
/s/ Helen H. GatesonTitle:
Vice PresidentWELLS FARGO BANK, NATIONAL
ASSOCIATION, as a BankBy:
    /s/ G. N. OphaugTitle:
    V.P. 3




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ACKNOWLEDGMENT Reference is made to the Guaranty, dated as of April 30, 2002 (the
Guaranty) pursuant to which the undersigned, as Guarantor (the Guarantor)
has guaranteed payment and performance of obligations of Otter Tail Corporation
(the Borrower) to U.S. Bank National Association, as Agent, and the Banks
(the Creditors) under the Credit Agreement among the Borrower and the
Creditors dated as of April 30, 2002 (as thereafter amended, the Credit
Agreement) and under each Note and Loan Document, as defined in the Credit
Agreement. The Guarantor acknowledges that it has received a copy of the
proposed Fourth Amendment to the Credit Agreement, to be dated on or about
April 28, 2004 (the Amendment). The Guarantor agrees and acknowledges that
the Amendment shall in no way impair or limit the right of the Creditors under
the Guaranty, and confirm that by the Guaranty, the Guarantor continues to
guaranty payment and performance of the obligations of the Borrower to the Bank
under the Credit Agreement as amended pursuant to the Amendment. The Guarantor
hereby confirms that the Guaranty remains in full force and effect, enforceable
against the Guarantor in accordance with its terms. Dated as of April 28, 2004. VARISTAR CORPORATIONBy:
    /s/ Kevin G. MougTitle:
    CFO