Lambert becomes the latest "American Idol" alum to join the Fox musical. Last season, "Idol" runner-up Jessica Sanchez had a multiple-episode role on the Ohio-set side of the series, playing a diva singer at a rival glee club.
For the season eight Idol runner-up, the "Glee" gig marks a dream come true. The singer told The Hollywood Reporter in January 2012 that he feels the scripted singing series is "so cute" and "really paints a picture of what it's like to be an arts kid in high school."
"'Glee' is really irresistible -- it's charming," he said at the time, noting he'd love to be able to play himself on the series. (Lambert most recently played himself and performed on ABC Family's "Pretty Little Liars.")
Lambert's casting marks a welcome injection of star power to "Glee." The series will see some of its original cast members -- fan favorites Heather Morris, Mark Salling, Amber Riley and Harry Shum Jr. -- take on a reduced role next season. To compensate, the show bumped up to series regulars new additions Melissa Benoist, Jacob Artist, Becca Tobin, Blake Jenner and Alex Newell to series regulars.
"Glee" has a history of booking big-name guest stars. Sarah Jessica Parker and Kate Hudson both had recurring roles during Glee's fourth season as the series split its focus between its Ohio-set high school and New York, where stars Lea Michele and Chris Colfer are prominently featured.
"Glee" returns with its fifth season Thursday, Sept. 19 at 9 p.m. on Fox.