The singer and actress will star in the NBC pilot which revolves around a group who team together to stage a Broadway show based on the life on Marilyn Monroe, says The Hollywood Reporter.
Details of McPhee's character have not been announced, although it has been confirmed that former Will & Grace star Debra Messing will play the production's lyricist, and that Jack Davenport will appear as the choreographer.
Spielberg is among the executive producers of Smash.
McPhee shot to fame on American Idol, where she finished runner-up on the fifth season. She has since appeared in movies including The House Bunny and guest starred in TV shows such as CSI: NY and Community.