Austin Howard finished with 250 yards passing and a touchdown for the Jaguars (5-3, 4-1 SWAC).
Tillery's 77-yard scoring run came with 4:45 left in the first quarter. Earlier, Deonte Shorts ran it in from 5 yards for the first Southern touchdown and Willie Quinn scored on an 81-yard punt return and the Jaguars had a 21-0 advantage by the end of the first quarter.
Late in the second quarter, Jaleel Richardson scored on a 97-yard kickoff return.
Ivy threw for 424 yards and three touchdowns for the Tigers (3-5, 1-4).