As a true freshman in 2011, O’Leary played in all 13 games with two starts. He finished the season with 12 receptions for 164 yards and one touchdown. As a sophomore in 2012, he started 11 of 13 games, recording 21 receptions for 252 yards and three touchdowns. As a junior in 2013, he was a John Mackey Award finalist after recording 33 receptions for 557 yards with seven touchdowns. After considering entering the 2014 NFL Draft, O’Leary returned to Florida State for his senior season. During his senior season he set Florida State’s record for career receptions for a tight end. He again was a finalst for the John Mackey Award, this time winning it. He was also named a consensus All-American. O’Leary finished the season with 48 receptions for 618 yards and six touchdowns. For his career he had 114 receptions for 1,591 yards and 17 touchdowns.