In the two previous weeks, Wallace had seen his Heisman Trophy hopes take a major hit by throwing for a combined 269 yards in losses to nationally ranked Oklahoma and Texas.
But the electrifying quarterback bounced back against the Tigers, setting a school ecord for completions while 31 of 47 for 425 yards and a touchdown. He also rushed for 68 yards on 10 attempts.
Wallace came up huge on the Cyclones' game-winning, 15-play, 93-yard drive with runs of 11 and 33 yards. Michael Wagner capped the drive with a one-yard run with 32 seconds remaining, giving Iowa State (7-3, 4-2) a 42-35 lead.
Freshman Brad Smith passed for 228 yards and a touchdown for Missouri (4-5, 1-4), which lost for the fourth time in its last five games.