I think my biggest disappointing loss was the 1979 Holiday Bowl against Indiana. BYU was undefeated in the regular season that year at 11-0, while Indiana finished 4th place in the Big Ten and 8-4 overall. I’m guessing the Cougars were heavy favorites.
BYU had lots of turnovers and penalties that game. They seemed to be totally out of sync. (Credit Coach Lee Corso for having the Hoosiers ready to play)
BYU, despite really underperforming in my opinion, had a chance to win the game in the last seconds with a chip shot field goal. Sadly, our kicker missed it. Indiana won 38-37.