Miller said the event was reported to him on July 11 by Dan Tangherlini, the agency's acting administrator.
"This sounds almost unbelievable to have this kind of waste reported when we are running trillions of dollars in debt," said Transportation and Infrastructure Committee Chairman John Mica (R., Fla.).
The GSA said in a statement that all spending for events had been suspended in April.
"Under the new GSA leadership, this event and type of spending is not tolerated," said agency spokeswoman Betsaida Alcantara.
The new revelation comes after government watchdogs found that GSA officials in Western states went on taxpayer-financed junkets to Hawaii, South Pacific islands, and California's Napa Valley and Palm Springs, where they stayed at resort hotels and threw lavish parties.
The loudest outcry was over a 2010 Las Vegas conference, which featured a clown, mind reader and a rap video making fun of the excessive spending. The event for 300 employees cost $823,000, Miller reported.
"You can see they are classing up their act, but it's still a blatant abuse of taxpayer dollars," said subcommittee chairman Jeff Denham.
In his letter to the House Economic Development, Public Buildings and Emergency Management Subcommittee, Miller said his preliminary investigation shows the event cost more than $268,732 for the one-day ceremony, which took place at the Crystal Gateway Marriott, and a "commissioner's reception" for 200 attendees was held at the Key Bridge Marriott the same day, he reported.