The 34-year-old American Idol alum cozied up to Foster, 68, wearing a sexy pink silk dress.
The couple attended the Carousel Of Hope Ball in aid of the Children's Diabetes Foundation and the Barbara Davis Center for Childhood Diabetes on Saturday evening.
McPhee wore nude colored high-heels and her brunette hair was cut into a bob with a fringe to suit her vintage style dress.
Her handsome beau suited up in a classic black tuxedo with a white dress shirt and black bow tie.
He took the piano to accompany singer Gladys Knight who sang 'Midnight Train To Georgia' and 'Best Thing That Ever Happened To Me' plus a cover of Sam Smith's 'Stay With Me'.
McPhee and Foster got engaged over the summer.
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