Entertainment Weekly reports that the actor will portray a character named Bud Mayberry.
Mayberry, the leader of a polygamist fringe group, will apparently encounter Bill (Bill Paxton) shortly after he joins the Utah State Senate.
Patrick is known for his role as the T-1000 in Terminator 2: Judgement Day and also played John Doggett on The X-Files from 2000 to 2002. His recent television roles include guest appearances in Chuck and Burn Notice.
The fifth season of Big Love is expected to begin early next year on HBO.