The cast of "Glee' performed on "The X Factor" this weekend -- without the help of auto-tune!

Lea Michele, Cory Monteith, Jenna Ushkowitz, Kevin McHale, Amber Riley, Dianna Agron, Naya Rivera, Mark Salling, Heather Morris, Harry Shum Jr. and newcomer Chord Overstreet all hit the stage to perform for Simon Cowell on the UK show.

Chris Colfer couldn't make the trip because he was shooting scenes with Darren Criss and The Warblers.

The gang sang "Don't Stop Believin'" -- which just earned them a Grammy nomination.

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