The comedy, which is currently untitled, stars Damon Wayans as a popular sports radio host called Nick.
According to Deadline, McWilliams has now joined the cast as Nick's wife Megan.
Megan has two children from a previous marriage and is a stepmother to Nick's son. She is said to be a well-educated businesswoman who is starting to get frustrated that she has given up her career to look after the family.
McWilliams starred as Kaycee in Prison Break and worked on the movie The Lake House. More recently, she has been appearing as Lilly in The Chicago Code.
The CBS project, which has been inspired by ESPN personality Colin Cowherd, will also star Eliza Dushku and Danny Comden.