After two years in New York City, Carmack decided to move to Los Angeles and immerse himself in acting. He is best known by global audiences as Luke on the first season of The O.C., but did not continue because producers could not guarantee him airtime in the upcoming year. In 2005, Carmack became a model for Ezra Fitch, a limited upscale label sold at Abercrombie & Fitch.
In 2006 Carmack made his London stage debut in a rare revival of Tennessee Williams' Summer and Smoke, a play unperformed in London for 55 years. Carmack starred opposite Rosamund Pike and was directed by former Royal Shakespeare Company artistic Director Adrian Noble. It played the Apollo Theatre from 21 October–25 November 2006, failing to complete its scheduled run.
Carmack portrayed Sam Reide, the main character of the film The Butterfly Effect 3: Revelations, the third film in The Butterfly Effect film franchise, released in theaters in January 2009. He also made his first voice role in Alpha and Omega, which was released in theaters in September 17, 2010, and reprised his role as Garth in Alpha and Omega 2: A Howl-iday Adventure, being one of the few actors from the original to appear in at least one sequel.
The Music of Nashville: Season 2, Volume 1 (2013)
The Music of Nashville: Season 3, Volume 1 (2014)
The Music of Nashville: Season 4, Volume 1 (2015)
The Music of Nashville: Season 4, Volume 2 (2016)
The Music of Nashville: Season 5, Volume 3 (2017)
