In his first three seasons (2008–2010), he totaled 1,849 all-purpose yards, including 1,156 receiving yards and 694 return yards. On October 1, 2011, he had a career-best performance against Northwestern, with 12 catches for 268 yards and three touchdowns. His performance against Northwestern broke the Illinois single-game receiving record, ranks fourth in Big Ten Conference history, and earned him Big Ten Offensive Player of the Week after the Northwestern game. Through the first 11 games of his senior season, Jenkins had 1,166 receiving yards and seven touchdown receptions.
As of November 20, 2011, Jenkins' 1,166 receiving yards during the 2011 season ranked second in the Big Ten Conference and 11th among NCAA Division I FBS players. At the conclusion of the 2011 season, Jenkins was named First Team All-Big Ten by both the coaches and media.
Although healthy all season, Jenkins was active for only three of the 49ers 16 regular season games. In his rookie regular season he played in only 37 offensive snaps and was targeted with a pass just once, which he dropped.