Katharine McPhee & Fiance David Foster Step Out to Celebrate Simon Cowell's Star on the Walk of Fame!

Katharine McPhee and David Foster are celebrating!

The Waitress star and the music producer were spotted heading in to attend Simon Cowell‘s party to celebrate his star on the Hollywood Walk of Fame on Wednesday evening (August 22) at Ago in West Hollywood, Calif.

PHOTOS: Check out the latest pics of Katharine McPhee

Kat and David looked happy to celebrate the big honor as they made their way into the restaurant.

The two also attended the actual Walk of Fame ceremony earlier in the day alongside American Idol alums like Adam Lambert, Kelly Clarkson and Harry Connick Jr. in Hollywood, Calif.