We are a small consulting business (3 partners and 1 employee).  We
have received some contract work from a receipient of a Federal Grant,
and they have asked us, and subrecipients, for evidence of a "FAR-Part
30" audit.  I am hoping that as a small business we might be exempt
from such an audit.  Are we?  If so, what's the exemption clause? if
not, how would we go about getting the audit?

gzw, I have good news!  (And no, I didn't just save a bunch of money
by...never mind.)
Looks as though you are exempt:
FAR is the Federal Acquisition Regulations.  FAR Part 30 states that
the Cost Accounting Standards do not apply to a contract with a small
business:
"30.000  Scope of part. 
This part describes policies and procedures for applying the Cost
Accounting Standards Board (CASB) rules and regulations (48 CFR
Chapter 99 (FAR Appendix)) to negotiated contracts and subcontracts.
This part does not apply to sealed bid contracts or to any contract
with a small business concern (see 48 CFR 9903.201-1(b) (FAR Appendix)
for these and other exemptions)."
http://www.arnet.gov/far/current/html/Subpart%2030_1.html#wp1068566

Since FAR Part 30 refers to 48 CFR 9903.201-1(b), I thought it prudent
to look there too.  That's the part of the Code of Federal Regulations
that discusses exemptions to the Cost Accounting Standards.  Sure
enough, small businesses are exempt.

"Sec. 9903.201-1  CAS applicability.
    (a) This subsection describes the rules for determining whether a 
proposed contract or subcontract is exempt from CAS. (See 9904 or 9905, 
as applicable.) Negotiated contracts not exempt in accordance with 
9903.201-1(b) shall be subject to CAS.
(b) The following categories of contracts and subcontracts are 
exempt from all CAS requirements:
?
(3) Contracts and subcontracts with small businesses."

http://a257.g.akamaitech.net/7/257/2422/12feb20041500/edocket.access.gpo.gov/cfr_2004/octqtr/48cfr9903.201-1.htm

Best of luck with your business.

Excellent, thank you so much!