Collier redshirted during his first season at TCU, but became a starter for the Horned Frogs as a redshirt freshman in 2015 despite appearing in just one game. He played in all 13 games for the Horned Frogs as sophomore, recording 4.5 sacks and blocking a field goal against Georgia in the 2016 Liberty Bowl. He recorded 4.5 sacks again as a junior, including one in a crucial late-game situation in the Frogs' comeback win over Stanford in the 2017 Alamo Bowl.
