Williamson played in every game, starting five contests as a true freshman. He caught 17 passes for 491 yards (28.9 avg.) and four touchdowns while adding 47 yards on three carries (15.7 avg.) and 74 yards on three kickoff returns (24.7 avg.). In 2003, Williamson started 10 games at split end. He hauled in 31 passes for 428 yards (13.8 avg.) and two touchdowns, including a school- and Southeastern Conference-record 99-yarder. He also handled the bulk of the team's kickoff return duties, gaining 268 yards on 14 attempts (19.1 avg.).
As a junior, Williamson accounted for a career-high 835 yards on 43 receptions with seven touchdowns. He also had seven kickoff returns for 105 yards (15.0 avg.) and 30 yards on four carries (7.5 avg.). He closed out his career with 91 receptions for 1,754 yards (19.3 avg.) and 13 touchdowns in 34 games. His 1,754 yards rank seventh on the school's all-time record list. Williamson also gained 101 yards on 12 carries (8.4 avg.), 447 yards on 24 kickoff returns (18.6 avg.) and recorded four solo tackles on special teams.