From 2005 to 2008, he codirected, co-wrote and coproduced the Adult Swim stop-motion animation program Moral Orel with Dino Stamatopoulos and Jay Johnston.

Adsit is known for his role as Pete Hornberger, the well-meaning but jaded producer, on the NBC sitcom 30 Rock, which won a Screen Actors Guild Award for Outstanding Performance by an Ensemble in a Comedy Series in 2008.

He appeared in several Joseph Jefferson Award-winning revues, including Piñata Full of Bees and Paradigm Lost for which he won The Jeff Award for Best Actor in a Comedy.

A sketch he performed with future Saturday Night Live head writer Adam McKay, "Gump," was included as one of Second City's all-time best in the theater's 25th anniversary compilation.

He appeared in the 1997 PBS documentary about the process of creating the Second City review, Paradigm Lost, Second to None along with castmates Tina Fey, Kevin Dorff, Rachel Dratch, Jenna Jolovitz and Jim Zulevic.

[7] In 1996, he portrayed an alcoholic and drug-addicted father in Minnesota's Hazelden Substance Abuse Clinic short-subject production, Reflections From The Heart Of A Child.

[8] This 26-minute video/DVD feature has become required curriculum in most DWI Repeat Offender classes and substance abuse rehabilitation clinics across the U.S.[9] In 1997, Adsit recorded the voices for the King of Payne, Sir Psycho, The Duke of Bourbon, and Merlin for Williams' Medieval Madness pinball machine.

[10] In 1998, Adsit moved to Los Angeles after an invitation from his college friend Dino Stamatopoulos to work on a pilot about the backstage antics of a television sketch-comedy variety show.

In a twist of fate, he also auditioned for Aaron Sorkin's Studio 60 on the Sunset Strip, another series about the behind-the-scenes drama of a variety show.

After the success of Moral Orel, Adsit and Dino Stamatopoulos worked together again on their newest stop-motion animation series Mary Shelley's Frankenhole, which first aired on Adult Swim on June 27, 2010 and ran for a total of 20 episodes over 2 seasons.

[13] In June 2010, Adsit hosted a panel featuring comic book writers Dan Slott, Frank Tieri, and Chris Claremont at HeroCon in Charlotte, North Carolina.

"[21][22][23] Adsit joined the Season 3 cast of the Adult Swim live-action TV series The Heart, She Holler as the corrupt Sheriff, starring alongside Amy Sedaris.