Among the groups being probed is Help Hospitalized Veterans, which was founded in 1971 by Roger Chapin, The Washington Post reported.
The newspaper reviewed the non-profits tax reports and found in collected $71.3 million in the last fiscal year. It also paid $3.8 million in salary and benefits to Chapin and his wife from 1997 to 2005 and spent more than $200 million on fundraising during the same period.
Committee member Rep. Chris Van Hollen, D-Md., told the Post the inquiry was meant to distinguish between charities that genuinely serve veterans and those "committing fraud against the public."
Chapin, 75, was scheduled to testify Thursday, and told the Post he wasn't pleased.
"You don't know me but these guys have got this thing so wrong, it's unbelievable," Chapin said. "It's a witch hunt. They're totally misrepresenting what the facts are."