McMahon was one of eight former Cougar All-America quarterbacks honored at halftime, along with Virgil Carter, Gifford Nielsen, Marc Wilson, Steve Young, Robbie Bosco, Ty Detmer and Steve Sarkisian.
Joining them was legendary coach LaVell Edwards.
Sarkisian, who was coaching Washington, remained in the locker room at halftime with his team nursing a 17-13 edge.
"This has been the first time all eight of us have been together. It's been a great weekend," Young said. "We're gathered here because we bleed Cougar blue. ... We want Bronco to know we embrace him and his team."
The school announced that during the weekend's "Y Quarterback" festivities more than $1 million was raised for athletic scholarship endowments.