Glee celebrates a milestone on Tuesday night.

During the episode "Mash Off," Shelby's new all-female choir will take to the stage and do a lot more than merely mash-up two Adele singles; the group will perform the show's 300th musical number! That's almost as many songs as Sue Sylvester one-liners.

Watch Santana and Mercedes take the lead below, as Shelby looks on proudly and Will looks on in fear:

Glee Cast - Adele Mash Up

What else can fans expect on the episode? View the official trailer HERE to find out!

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.