OSI Restaurant Partners Incorporated said yesterday it has agreed to a $40-a-share buyout led by two private-equity firms in a move that will give the multi-concepts casual-dining company more “runway” to fix problems at its Outback Steakhouse.

Terms call for investors led by Bain Capital LLC and Catterton Partners to pay about $3 billion, excluding assumption of debt, for the Tampa restaurateur. With debt, OSI valued the transaction, which requires shareholder approval, at $3.2 billion.

The $40 share price represents a 23.3% premium over Friday’s closing of $32.43. The stock hit a 52-week high of $48.28 last Feb. 2. Its 52-week low was $27.30, on July 31.

The NYSE-listed stock was trading recently at $40.08, up $7.65, or 23.6%, on composite volume of 7.8 million shares, more than nine times the daily average volume.

Besides Bain and Catterton, the investor group includes company founders Chris Sullivan, Robert Basham, and J. Timothy Gannon. Stakes are expected to be disclosed in a filing with the Securities and Exchange Commission later Monday. The agreement to go private calls for OSI to solicit “superior proposals” from other parties for the next 50 days, a move “to insure that shareholders are getting full and fair value,” the chief executive, Bill Allen, told Dow Jones Newswires, but indicated that OSI’s board and management considered the current offer “a great win for our shareholders.”