Travon Langston gave the Thunderbirds the lead for good at 75-73 on a breakaway layup with 38 seconds left in overtime. Juwan Major added a free throw with 26.7 seconds that capped a 6-0 run for Southern Utah (8-17, 5-9 Big Sky).
Wiggs nailed a 3-pointer with 11 seconds left in the second half to send the game to overtime tied at 69.
McGee was 5 of 8 from 3-point range and Cal Hanks added 16 points and three blocks.
Wiggs led Idaho with 19 points.