Jarvion Franklin ran for 149 yards and a score for the Broncos (4-3, 2-1 Mid-American Conference).
Terrell's first scoring pass went to Corey Davis early in the second quarter to give Western Michigan its first lead of the game, 10-7. His second was a 63-yarder to Darius Phillips early in the third for a 19-14 advantage.
Bowling Green took an early 7-0 lead in the first quarter on a 2-yard run by Andre Givens. Givens scored again just before halftime and the Falcons (5-3, 3-1) led 14-13 at the break.
But the Broncos rallied in the second half with Terrell's TD pass to Phillips and Franklin's 22-yard rushing touchdown late in the fourth quarter.
The Falcons' James Knapke was 20-of-33 for 139 yards passing.