Grier was the Parade National High School Player of the Year in 2013 after throwing for 4,989 yards and a nation-best 77 touchdowns while also rushing for 1,251 yards and 13 scores. He played for his father, who was a backup quarterback at East Carolina and led Davidson Day School to multiple North Carolina state titles. Not surprisingly, Grier was highly-recruited, signing with Florida. He redshirted in 2014 and then started 5 of 6 games the following season, going 5-0 in those starts (106-161-65.8, 1,204 yards, 10 TD, three INT). He was suspended, however, for a year by the NCAA in October 2015, for taking a prohibited performance-enhancing supplement. While finishing out the suspension in 2016, Grier practiced with the Gators but wound up not playing at all during the year. Feeling unwanted by Florida coaches, he decided to transfer to West Virginia. Grier excelled in his first year with the Mountaineers, earning honorable mention All-Big 12 honors and ranking fifth in the FBS in passing efficiency, eighth with 34 passing TDs, and eighth with 317.3 passing yards per game (3,490 total). He completed 64.4 percent of his passes (250-388) while throwing 12 interceptions on the year. Grier was in the Heisman Trophy conversation most of his senior year, finishing among the national leaders in pass efficiency (175.5), touchdown passes (37), passing yards (3,864), and completion percentage (67.0, on 266-397 passing). He started 11 games in 2018 on his way to second-team All-Big 12 honors but skipped the team's bowl game to prepare for the draft.