Kickoff for the team's season opener is 2:37 p.m. at the Liberty Bowl.
Adams, who has been running with the first unit during the preseason, was selected over last year's starter, Brent Schaeffer, and redshirt freshman Michael Herrick.
"Since we opened the quarterback position in the spring, Seth has been the most consistent, both in the spring and in fall camp," Orgeron said in a statement. "Our quarterback position will be treated like any other position on the team. You have to earn your starting spot on a daily basis."
Adams, a 6-foot-4, 225-pounder from Holly Springs, walked on at Ole Miss in January of 2006 after transferring from Hinds Community College and participated in spring football drills.
Adams appeared in six games last year with significant time against LSU and Mississippi State. He completed 17 of 31 passes for 177 yards. But more significantly he showed the ability to calmly run the offense.
Schaeffer was inconsistent much of last season, completing 47.1 percent of his passes and throwing 10 interceptions and nine touchdowns.