Peter DuBois (Sons of the Prophet, Becky Shaw) will direct the July 18-29 run on the Vassar College campus.
Joining Kinnear ("Little Miss Sunshine," "As Good As It Gets") and Westfeldt (Wonderful Town, "Kissing Jessica Stein") will be Desmin Borges, Dominic Fumusa, Neil Huff, Russell G. Jones, Ben Platt and Maura Tierney.
Here's how the play is billed: "In The Power of Duff, Charles Duff (Kinnear), a news anchor in a mid-market backwater, has an unexpected spiritual awakening on live TV. His prayers, and their answers, change his audience, his family, and his own life forever."
Belber's plays include Tape, Match, Dusk Rings a Bell and Fault Lines.
For tickets, phone (845) 437-5599 or visit Powerhouse.Vassar.edu.