Kenny Stills dropped a pass and then right tackle Tyrus Thompson was called on a personal foul penalty for unnecessary roughness.
On third-and-23, Jones threw to Saunders near the 10-yard line and the junior took it the rest of the way for a 24-yard score.
“That was a huge play,” offensive coordinator Josh Heupel said. “Obviously you don't want to be behind the chains like we were. Protection was great based on the coverage you see pre-snap; that's probably not where you are going to go with the football.
“Landry does a great job reading it out and great job by Jalen continuing to work and flattening off and going against a linebacker.”
TCU safety Sam Carter blamed himself for the play, saying the missed coverage changed the game.
“I didn't do my job,” Carter said. “I felt I should have made a play right there, but I didn't.”
The reception was Saunders' third touchdown of the season.
“I just felt like one of us were going to break open sooner or later,” Saunders said. “I'm just real excited ... I never won a championship before.”