The conferences signed a five-year deal setting up such a game, although the champions of the leagues would meet only if both of them fail to make it into the four-team, national-championship playoff.
If one or both of the league champs are in contention for the national title, another team or teams from their conference will play in the bowl game. The first contest is scheduled for Jan. 1, 2015.
"A new January bowl tradition is born," said SEC Commissioner Mike Slive. "This new game will provide a great matchup between the two most successful conferences in the BCS era and will complement the exciting post-season atmosphere created by the new four-team (national championship) model.
"Most importantly, it will provide our student-athletes, coaches and fans with an outstanding bowl experience."
During the 14-year history of the Bowl Championship Series, SEC teams have played for the national title nine times and Big 12 schools have appeared in the championship game seven times.
No decision has been made as to the host site of the Big 12-SEC game.