Agron, who plays Quinn Fabray on the Fox musical series, will be the guest mentor on the Aug. 7 episode, "Actability." Gustin, who has been seen in the national tour of West Side Story and plays recurring cast member Sebastian Smythe on "Glee," will oversee the July 17 episode, "Theatricality."

Lea Michele, Samuel Larsen, Cory Monteith and Naya Rivera have been mentors for the second season  of "The Glee Project." Upcoming appearances include Amber Riley ("Tenacity"), Darren Criss ("Romanticality"), Chris Colfer ("Glee-ality") and Jane Lynch ("Fearlessness"). 

The show, which kicked off June 5 with Spring Awakening's Michele as the guest mentor, features 14 young performers competing for a multi-episode, guest-starring role on Fox's "Glee." "Glee" co-producer Ryan Murphy has confirmed that this season's "Glee Project" will only feature one winner as compared to last season's tie.

During the 11-week run of the series, according to Oxygen, "'The Glee Project' contenders will be narrowed down through intensive rounds of workshops, singing, dancing and acting-based assignments as the creative forces of ‘Glee’ carefully assess who has what it takes to be one of the next new faces of the award-winning show. Murphy will once again join casting director Robert Ulrich and choreographer and 'Glee' co-producer Zach Woodlee in the final deliberations of each installment of the series. Vocal coach Nikki Anders, who mentored the contenders on-air in season one, joins the judging panel in season two each week as a permanent member. Additionally, continuing with the format of season one, 'Glee' series regulars will appear on 'The Glee Project' as guest mentors."

Winners of the first season of "The Glee Project," Damian McGinty and Larsen, were featured on the third season of "Glee" as foreign-exchange student Rory Flanagan and religious transfer student Joe Hart, respectively. The runner-up contestants of the reality series, Alex Newell and Lindsay Pearce, were given a two-episode spotlight on "Glee." To meet the contestants of "The Glee Project," click here.