Tommy Lee Jones, Charlize Theron, Susan Sarandon and Jonathan Tucker already have been cast in the mystery thriller, which "Crash" filmmaker Paul Haggis is directing for Warner Independent Pictures.
"Valley," whose title is likely to change, follows a war veteran (Jones) in search of his son, an exemplary soldier who recently returned from Iraq and has gone AWOL.
Franco is playing a sergeant, Fisher a waitress, McGraw a police chief and Patric an Army lieutenant. Mehcad Brooks ("Desperate Housewives") has been cast as a member of the son's squad.
Franco will be seen in "Spider-Man 3" in the summer. Fisher recently wrapped shooting Dan Waters' "Sex and Death 101."
Country superstar McGraw most recently appeared in "Flicka." Patric next will be seen in "The Good Shepherd."