Exhibit 10.1

Execution Version

FOURTH AMENDMENT

TO

SECOND AMENDED AND RESTATED

CREDIT AGREEMENT

Dated as of April 15, 2009

AMONG

BILL BARRETT CORPORATION,

AS BORROWER,

THE GUARANTORS,

JPMORGAN CHASE BANK, N.A.

AS ADMINISTRATIVE AGENT,

AND

THE LENDERS PARTY HERETO

--------------------------------------------------------------------------------

FOURTH AMENDMENT TO SECOND AMENDED AND RESTATED CREDIT AGREEMENT

THIS FOURTH AMENDMENT TO SECOND AMENDED AND RESTATED CREDIT AGREEMENT (this
“Fourth Amendment”) dated as of April 15, 2009 is among BILL BARRETT
CORPORATION, a Delaware corporation (the “Borrower”), each of the undersigned
guarantors (the “Guarantors”, and together with the Borrower, the “Obligors”)’
each of the lenders party to the Credit Agreement referred to below
(collectively, the “Lenders”), and JPMORGAN CHASE BANK, N.A., as administrative
agent for the Lenders (in such capacity, together with its successors in such
capacity, the “Administrative Agent”).

R E C I T A L S

A. The Borrower, the Administrative Agent and the Lenders are parties to that
certain Second Amended and Restated Credit Agreement dated as of March 17, 2006
(as amended by the First Amendment to Second Amended and Restated Credit
Agreement dated November 6, 2007, the Second Amendment to Second Amended and
Restated Credit Agreement dated March 4, 2008, the Third Amendment to Second
Amended and Restated Credit Agreement dated October 20, 2008, and as further
amended, restated, modified or supplemented, the “Credit Agreement”), pursuant
to which the Lenders have made certain credit available to and on behalf of the
Borrower.

B. The Borrower has requested and the Administrative Agent and the
Super-Majority Lenders have agreed to make certain other changes to the Credit
Agreement.

C. NOW, THEREFORE, to induce the Administrative Agent and the Lenders to enter
into this Fourth Amendment and in consideration of the premises and the mutual
covenants herein contained, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

Section 1. Defined Terms. Each capitalized term used herein but not otherwise
defined herein has the meaning given such term in the Credit Agreement, as
amended by this Fourth Amendment. Unless otherwise indicated, all section
references in this Fourth Amendment refer to sections of the Credit Agreement.

Section 2. Amendments to Credit Agreement.

2.1 Amendments to Section 1.02.

(a) The following definition is hereby added where alphabetically appropriate to
read as follows:

“Fourth Amendment” means that certain Fourth Amendment to Second Amended and
Restated Credit Agreement, dated as of April 15, 2009 among the Borrower, the
Guarantors, the Administrative Agent and the Lenders party thereto.

--------------------------------------------------------------------------------

(b) The following definitions are hereby amended by deleting such definitions in
their entirety and replacing them with the following definitions:

“Agreement” means this Second Amended and Restated Credit Agreement, as amended
by the First Amendment, the Second Amendment, the Third Amendment and the Fourth
Amendment, including the Schedules and Exhibits hereto, as the same may be
amended or supplemented from time to time.

“Applicable Margin” means, for any day, with respect to any ABR Loan or
Eurodollar Loan, the rate per annum set forth in the Borrowing Base Utilization
Grid below based upon the Borrowing Base Utilization Percentage then in effect:

 

Borrowing Base

Utilization Percentage

   £ 50%     > 50% £ 75%     > 75% £ 90%     > 90%  

ABR Loans

   0.750 %   1.000 %   1.250 %   1.500 %

Eurodollar Loans

   1.750 %   2.000 %   2.250 %   2.500 %

Each change in the Applicable Margin shall apply during the period commencing on
the effective date of such change and ending on the date immediately preceding
the effective date of the next such change; provided, however, that if at any
time the Borrower fails to deliver a Reserve Report pursuant to Section 8.12(a),
then the “Applicable Margin” means the rate per annum set forth on the
applicable grid when the applicable Borrowing Base Utilization Percentage is at
its highest level; provided further that the Applicable Margin shall revert to
the previous Applicable Margin upon the Borrower’s delivery of such Reserve
Report.

“Defaulting Lender” means any Lender, as reasonably determined by the
Administrative Agent, that has (a) failed to fund any portion of its Loans or
participations in Letters of Credit within three (3) Business Days of the date
required to be funded by it hereunder, (b) notified the Borrower, the
Administrative Agent, the Issuing Bank or any Lender in writing that it does not
intend to comply with any of its funding obligations under this Agreement or has
made a public statement to the effect that it does not intend to comply with its
funding obligations under this Agreement, (c) failed, within three (3) Business
Days after request by the Administrative Agent, to confirm that it will comply
with the terms of this Agreement relating to its obligations to fund prospective
Loans and participations in then outstanding Letters of Credit; provided that
any such Lender shall cease to be a Defaulting Lender under this clause (c) upon
receipt of such confirmation by the Administrative Agent; (d) otherwise failed
to pay over to the Administrative Agent or any other Lender any other amount
required to be paid by it hereunder within three (3) Business Days of the date
when due, unless the subject of a good faith dispute, or (e) become the subject
of a bankruptcy or insolvency proceeding, or has had a receiver, conservator,
trustee or custodian appointed for it, or has taken any action in furtherance
of, or

 

2

--------------------------------------------------------------------------------

indicating its consent to, approval of or acquiescence in any such proceeding or
appointment or has a parent company that has become the subject of a bankruptcy
or insolvency proceeding, or has had a receiver, conservator, trustee or
custodian appointed for it, or has taken any action in furtherance of, or
indicating its consent to, approval of or acquiescence in any such proceeding or
appointment; provided that a Lender shall not be a Defaulting Lender solely by
virtue of the ownership or acquisition of any Equity Interest in such Lender or
a parent company thereof by a Governmental Authority or an instrumentality
thereof.

2.2 Amendment to Section 2.08. The following Subsection (k) shall be added to
the end of Section 2.08:

(k) Defaulting Lenders. Notwithstanding any provision of this Agreement to the
contrary, if any Lender becomes a Defaulting Lender, then the following
provisions shall apply for so long as such Lender is a Defaulting Lender:

(i) if any LC Exposure exists at the time a Lender is a Defaulting Lender, then
the Borrower shall within one Business Day following notice by the
Administrative Agent cash collateralize such Defaulting Lender’s LC Exposure in
accordance with the procedures set forth in Section 2.08(j) for so long as such
LC Exposure is outstanding;

(ii) if any Defaulting Lender’s LC Exposure is not cash collateralized as
required in Section 2.08(k)(i) above, then, without prejudice to any other
rights or remedies of the Issuing Bank or any Lender hereunder, all letter of
credit fees payable under Section 3.05(b) with respect to such Defaulting
Lender’s LC Exposure shall be payable to the Issuing Bank until such LC Exposure
is cash collateralized;

(iii) so long as any Lender is a Defaulting Lender, the Issuing Bank shall not
be required to issue, amend or increase any Letter of Credit, unless it is
satisfied that cash collateral will be provided by the Borrower in accordance
with Section 2.08(k)(i) above; and

(iv) for the avoidance of doubt, the Borrower shall retain and reserve its other
rights and remedies respecting each Defaulting Lender.

Section 3. Borrowing Base. For the period from and including April 15, 2009
until the next Redetermination Date, the Borrowing Base is $600,000,000.
Notwithstanding the foregoing, the Borrowing Base may be subject to further
adjustments from time to time pursuant to Section 2.07(e), Section 8.13(c),
Section 9.12(d) or Section 9.18.

Section 4. Conditions Precedent. This Fourth Amendment shall not become
effective until the date on which each of the following conditions is satisfied
(or waived in accordance with Section 12.02 of the Credit Agreement):

4.1 The Administrative Agent shall have received from the Super-Majority
Lenders, counterparts (in such number as may be requested by the Administrative
Agent) of this Fourth Amendment signed on behalf of such Person.

 

3

--------------------------------------------------------------------------------

4.2 No Default or Event of Default shall have occurred and be continuing as of
the date hereof, after giving effect to the terms of this Fourth Amendment.

The Administrative Agent is hereby authorized and directed to declare this
Fourth Amendment to be effective when it has received documents confirming or
certifying, to the satisfaction of the Administrative Agent, compliance with the
conditions set forth in this Section 4 or the waiver of such conditions as
permitted hereby. Such declaration shall be final, conclusive and binding upon
all parties to the Credit Agreement for all purposes.

Section 5. Miscellaneous.

5.1 Confirmation. The provisions of the Credit Agreement, as amended by this
Fourth Amendment, shall remain in full force and effect following the
effectiveness of this Fourth Amendment.

5.2 Ratification and Affirmation; Representations and Warranties. Each Obligor
hereby (a) acknowledges the terms of this Fourth Amendment; (b) ratifies and
affirms its obligations under, and acknowledges, renews and extends its
continued liability under, each Loan Document to which it is a party and agrees
that each Loan Document to which it is a party remains in full force and effect,
except as expressly amended hereby, notwithstanding the amendments contained
herein; and (c) represents and warrants to the Lenders that as of the date
hereof, after giving effect to the terms of this Fourth Amendment: (i) all of
the representations and warranties contained in each Loan Document to which it
is a party are true and correct, except to the extent any such representations
and warranties are expressly limited to an earlier date, in which case, such
representations and warranties shall continue to be true and correct as of such
specified earlier date, (ii) no Default or Event of Default has occurred and is
continuing, (iii) no event or events have occurred which individually or in the
aggregate could reasonably be expected to have a Material Adverse Effect and
(iv) the Mortgaged Properties represent at least 80% of the total value of the
Oil and Gas Properties evaluated in the most recently completed Reserve Report.

5.3 Counterparts. This Fourth Amendment may be executed by one or more of the
parties hereto in any number of separate counterparts, and all of such
counterparts taken together shall be deemed to constitute one and the same
instrument. Delivery of this Fourth Amendment by facsimile or electronic
transmission in portable document format (.pdf) shall be effective as delivery
of a manually executed counterpart hereof.

5.4 NO ORAL AGREEMENT. THIS FOURTH AMENDMENT, THE CREDIT AGREEMENT AND THE OTHER
LOAN DOCUMENTS EXECUTED IN CONNECTION HEREWITH AND THEREWITH REPRESENT THE FINAL
AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,
CONTEMPORANEOUS, OR UNWRITTEN ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO
SUBSEQUENT ORAL AGREEMENTS BETWEEN THE PARTIES.

 

4

--------------------------------------------------------------------------------

5.5 GOVERNING LAW. THIS FOURTH AMENDMENT (INCLUDING, BUT NOT LIMITED TO, THE
VALIDITY AND ENFORCEABILITY HEREOF) SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

5.6 Payment of Expenses. In accordance with Section 12.03 of the Credit
Agreement, the Borrower agrees to pay or reimburse the Administrative Agent for
all of its reasonable out-of-pocket costs and reasonable expenses incurred in
connection with this Fourth Amendment, any other documents prepared in
connection herewith and the transactions contemplated hereby, including, without
limitation, the reasonable fees and disbursements of counsel to the
Administrative Agent.

5.7 Severability. Any provision of this Fourth 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 provisions hereof, and any such prohibition or unenforceability in any
jurisdiction shall not invalidate or render unenforceable such provision in any
other jurisdiction.

5.8 Successors and Assigns. This Agreement shall be binding upon and inure to
the benefit of the parties hereto and their respective successors and assigns.

[SIGNATURES BEGIN NEXT PAGE]

 

5

--------------------------------------------------------------------------------

IN WITNESS WHEREOF, the parties hereto have caused this Fourth Amendment to be
duly executed as of the date first written above.

 

BORROWER:     BILL BARRETT CORPORATION     By:   /s/ Robert W. Howard     Name:
  Robert W. Howard     Title:   Chief Financial Officer GUARANTORS:     CIRCLE B
LAND COMPANY LLC     By:   /s/ Robert W. Howard     Name:   Robert W. Howard    
Title:   Chief Financial Officer     BILL BARRETT CBM CORPORATION     By:   /s/
Robert W. Howard     Name:   Robert W. Howard     Title:   Chief Financial
Officer     BILL BARRETT CBM, LLC     By:   BILL BARRETT CBM CORPORATION, as
manager     By:   /s/ Robert W. Howard     Name:   Robert W. Howard     Title:  
Chief Financial Officer

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-1

--------------------------------------------------------------------------------

JPMORGAN CHASE BANK, N.A., as

Administrative Agent and Lender

By:   /s/ Ryan Fuessel Name:   Ryan Fuessel Title:   Senior Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-2

--------------------------------------------------------------------------------

BANK OF AMERICA, N.A., as a Lender By:   /s/ Stephen J. Hoffman Name:   Stephen
J. Hoffman Title:   Managing Director

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-3

--------------------------------------------------------------------------------

DEUTSCHE BANK TRUST COMPANY

AMERICAS, as a Lender

By:   /s/ Dusan Lazaroy Name:   Dusan Lazaroy Title:   Vice President By:   /s/
Michael M. Meagher Name:   Michael M. Meagher Title:   Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-4

--------------------------------------------------------------------------------

U.S. BANK NATIONAL ASSOCIATION,

as a Lender

By:   /s/ Daria Mahoney Name:   Daria Mahoney Title:   Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-5

--------------------------------------------------------------------------------

BMO CAPITAL MARKETS FINANCING, INC.

f/k/a Harris Nesbitt Financing, Inc., as a Lender

By:   /s/ Gumaro Tijerina Name:   Gumaro Tijerina Title:   Director

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-6

--------------------------------------------------------------------------------

BARCLAYS BANK plc, as a Lender By:   /s/ Maria Lund Name:   Maria Lund Title:  
Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-7

--------------------------------------------------------------------------------

FORTIS CAPITAL CORP., as a Lender By:   /s/ David Montgomery Name:   David
Montgomery Title:   Director By:   /s/ Ilene Fowler Name:   Ilene Fowler Title:
  Director

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-8

--------------------------------------------------------------------------------

WELLS FARGO BANK, N.A., as a Lender By:   /s/ Oleg Kogan Name:   Oleg Kogan
Title:   Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-9

--------------------------------------------------------------------------------

BANK OF SCOTLAND plc, as a Lender By:     Name:   Title:  

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-10

--------------------------------------------------------------------------------

GE BUSINESS FINANCIAL SERVICES INC.

FKA MERRILL LYNCH BUSINESS FINANCIAL SERVICES INC., as a Lender

By:   /s/ Brian P. Ward Name:   Brian P. Ward Title:   Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-11

--------------------------------------------------------------------------------

SUNTRUST BANK, as a Lender By:   /s/ David Simpson Name:   David Simpson Title:
  Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-12

--------------------------------------------------------------------------------

UNION BANK, N.A. (formerly known as UNION BANK OF CALIFORNIA, N.A., as a Lender)
By:   /s/ Whitney Randolph Name:   Whitney Randolph Title:   Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-13

--------------------------------------------------------------------------------

COMPASS BANK, as a Lender By:   /s/ Greg Determann Name:   Greg Determann Title:
  Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-14

--------------------------------------------------------------------------------

COMERICA BANK, as a Lender By:   /s/ Matt Turner Name:   Matt Turner Title:  
Corporate Banking Officer

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-15

--------------------------------------------------------------------------------

CREDIT SUISSE, CAYMAN ISLANDS BRANCH as a Lender By:   /s/ Nupur Kumar Name:  
Nupur Kumar Title:   Vice President By:   /s/ Shaheen Malik Name:   Shaheen
Malik Title:   Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-16

--------------------------------------------------------------------------------

GUARANTY BANK AND TRUST COMPANY, as a Lender By:   /s/ Gail J. Nofsinger Name:  
Gail J. Nofsinger Title:   Senior Vice President

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-17

--------------------------------------------------------------------------------

GOLDMAN SACHS CREDIT PARTNERS L.P., as a Lender By:   /s/ Andrew Caditz Name:  
Andrew Caditz Title:   Authorized Signatory

 

SIGNATURE PAGE TO FOURTH AMENDMENT TO

SECOND AMENDED AND RESTATED CREDIT AGREEMENT

S-18