With a 21-point lead on No. 20 Washington State with about 8 minutes to play in the fourth quarter, the Broncos appeared headed for another signature upset.
Then a pair of late mistakes in regulation let the Cougars back in the game and led to their eventual 47-44 victory in triple overtime.
Boise State backup quarterback Montell Cozart — who took over in the first quarter for an injured Brett Rypien — attempted a shovel pass as he was being tackled with under 6 minutes left in the fourth quarter and the Broncos up 31-17.
Washington State linebacker Peyton Pelluer stepped in front of that pass for the pick six, pulling the Cougars within 31-24 with 5:51 remaining.