They do have congressional oversight - at least 4 (twice to House and twice to Senate) times a year (see former Humphrey-Hawkins testimony)... By the way, today was the first day of Fed Chair Janet Yellen's testimony to Congress as part of this process : What to expect after Yellen's statement - CNBC, 2015 February 24
Audit the Fed is nowhere near "oversight" - check again the link I provided before ( It's Official: Ron Paul Is Head Of Monetary Policy Subcommittee - FR, post #99, 2010 December 09 (acorn/tree) ) ... Just replace "Ron" with "Rand" and you'll see the difference between oversight which has been long in place and outright control / takeover of monetary system by politicians.
Audit the Fed is stupid and not benign, and if it came from Democrats, most on FR would rightly be screaming "hijacking" and "politicizing" the Fed (whatever minor political biases they may have now are of human nature and can't be totally eliminated - that's why the Fed was layered that way, to minimize politics and maximize economics). Congressional takeover of monetary policy is not a solution, it is a problem to be avoided at all costs, just like takeover of Internet in the US by the FCC, under the "benign" guise of Net Neutrality.
Ron Paul has been embarrassed several times by Bernanke during these hearings' exchanges, I hope Rand Paul becomes as transparent to conservatives as his father was.
If FED is doing nothing bad, there should be no fear of an Audit. It is really not complicated.
An audit is NOT TAKING CONTROL. It is simply a report.