DeOssie played college football for the Brown Bears as a linebacker, which was the position he was selected as by the Giants during the fourth round of the 2007 NFL draft.

DeOssie would change positions after the team needed an emergency long snapper midway during his rookie season and remained there for the rest of his career.

He is the son of former NFL linebacker Steve DeOssie; the two hold the distinction of being the first father-son duo to win Super Bowls with the same franchise.

[1] DeOssie played in 36 games with 29 starts at Brown and recorded 315 tackles (187 solos) with 10.5 sacks, 36.5 stops for losses, 5 quarterback pressures, 5 forced fumbles, 11 deflected passes and 1 blocked kick and 4 interceptions for 60 yards in returns.

As a senior, he was a First-team All-Ivy League for the third consecutive season, he started all 10 games at strongside inside linebacker and he led the Bears with a career-high 110 tackles including 68 solo stops.

[3] He mostly played on special teams during his rookie season, taking over as the long snapper when starter Ryan Kuehl was placed on injured reserve midway through the year.

He continued to share the long snapping duties with Jay Alford and was chosen by Philadelphia Eagles head coach Andy Reid as a need player in the 2009 Pro Bowl.

On January 22, 2012, the Giants won the National Conference title with an overtime win against the San Francisco 49ers on a field goal breaking the 17–17 tie.