Mason announced the suspension Thursday before the Commodores open fall camp and would not say what Wallace did.
The Commodores have senior Kyle Shurmur returning as the starting quarterback. Among Vanderbilt's other quarterbacks, Mo Hasan played at Coffeyville Community College last season after transferring from Syracuse, and Allan Walters is a freshman.
Mason says he expects Wallace back in January.
The sophomore quarterback was not in the media guide handed out Thursday, according to The Tennessean. Wallace also is not listed on the team roster on Vanderbilt's website.