Two of Manziel's touchdown passes went to Uzoma Nwachukwu. All four of Nwachukwu's receptions this season have been for touchdowns.
The Aggies (2-1) were up 14-7 after the first quarter before Manziel scored on runs of 39 and 20 yards to give A&M a commanding lead.
Ben Malena had two rushing touchdowns in the first half and Texas A&M led 49-7 at halftime.
Dustin Harris had a 96-yard punt return for a touchdown and finished with a school and Southeastern Conference record 246 punt return yards for A&M.
Richard Cue threw for 189 yards and a touchdown for South Carolina St. (1-3) of the Football Championship Subdivision.