Agron - who stars as series regular Quinn Fabray in the Fox comedy - will appear in the August 7 episode on Oxygen, states The Hollywood Reporter.
Recurring star Grant Gustin (Sebastian) will also make his debut on the reality series on July 17.
The Glee Project will see its champion win a seven-episode arc on Glee during its fourth season.
Lea Michele, Cory Monteith, Naya Rivera and Kevin McHale have all appeared as guest mentors in the past, while Jane Lynch will star in tonight's episode.
Amber Riley and Darren Criss will appear in upcoming episodes, while Chris Colfer will join as a mentor for the second season's finale on August 17.
The fourth season of Glee will premiere on September 13 on Fox.
