Grassley asked the firms, including the politically connected Ballard Spahr firm, to detail how much money they have billed PHA since 2003.
Since 2007, PHA has paid roughly $33 million to 15 firms, including $9 million to Ballard Spahr, the former firm of Gov. Rendell, and $8.3 million to Wolf Block, before it disbanded in 2009.
Grassley wanted more than numbers.
He requested "any written summaries or reports of its work," including attachments or exhibits.
He also asked for a list of attorneys who performed the work, and completion dates. He gave the firms until Jan. 31.
Grassley's committee has been scrutinizing spending by public-housing agencies.
Grassley zeroed in on Philadelphia after allegations surfaced last year that former PHA Executive Director Carl Greene secretly settled three sexual-harassment complaints against him for a total of $648,000.
"The local housing authority reportedly has a record of trying to cover its tracks where it's spent tax dollars either inappropriately or in a way that would embarrass its leadership," Grassley said.
"And, the federal agency that provides most of the money that local housing authorities have to spend[spend] has continued to provide tax dollars even after it's clear that there's not responsible stewardship of those dollars."
Grassley added, "Both situations are an affront to taxpayers, and taxpayers deserve an accounting of what's gone on so that it can be stopped."
HUD's Office of Inspector General is conducting two audits of PHA: One focuses on money spent on PHA homes across the city; the other, on the agency's finances, including contracts awarded to law firms.