Oklahoma State
The last time Oklahoma State and BYU played each other was back in 1976 when BYU was just starting to build up their football brand.
Oklahoma State is a team that would be a really game for BYU. The Cowboys always tend to be ranked somewhere between 10 and 20 which would give the Cougars a tough but not impossible opponent. Oklahoma State would be the kind of game that if BYU won it would give them a lot of credit, and if they lost it wouldn’t do anything to hurt their reputation.
Also, Oklahoma State runs a really fun almost air-raid offense that would be a great matchup for BYU’s “drop eight” strategy.