The half-hour project - from Will & Grace creators Max Mutchnick and David Kohan - will focus on a straight man and a gay man who are friends and business partners.
Bush will play the straight man's girlfriend, according to Deadline.
The actress is best known for playing Brooke Davis on The CW's One Tree Hill, which will conclude later this year.
She has also appeared in such films as 2006's John Tucker Must Die, 2007's remake of The Hitcher and last year's Chalet Girl.
Mike & Molly director James Burrows will helm the Partners pilot.
Other comedy pilots in the works at CBS include Super Fun Night starring Bridesmaids actress Rebel Wilson and an untitled comedy from comedian Louis CK.
> Bridesmaids star Melissa McCarthy comedy pilot picked up by CBS