Oxford, the Class 6A state champion a year ago, finished its season 18-17.
The Yellow Jackets and Grissom split a doubleheader Friday, forcing a winner-take-all game in their best-of-three series today.
Grissom shot out to a 5-0 lead before Oxford managed three runs in the sixth inning. Trent Simpson slugged a home run, his 10th of the season. Matt Butler followed with a two-run single.
Joe McGuire brought home a run in the seventh inning with a sacrifice fly.