The Paul Haggis-helmed picture -- which already counted Tommy Lee Jones, Charlize Theron and Susan Sarandon among its cast -- also added James Franco, Frances Fisher and Mehcad Brooks, the Hollywood Reporter said.
"Valley of Elah" focuses on a war veteran, played by Jones, who is searching for his son who disappeared after returning home from serving in Iraq.
McGraw has been signed to play a police chief and Fisher a waitress in the production.
Filming is under way in New Mexico.
2014: The Year in Music [PHOTOS]