Wallace went 15-for-22 through the air for 294 yards for the Rebels (6-6, 3-5 SEC), who scored 24 unanswered points in the second half.
Donte Moncrief hauled down seven passes for 173 yards and three touchdowns as Mississippi became bowl eligible for the first time since 2009.
The Bulldogs (8-4, 4-4), meanwhile, finished the season by dropping four of their last five games as Tyler Russell was held to 18-of-33 passing efficiency for 268 yards, one touchdown and two interceptions.
Chad Bumphis led Mississippi State's receiving corps with six catches for 146 yards and two touchdowns.
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