The film, which stars John Krasinski and Maya Rudolph, is about a young couple who travel around the U.S. searching for a place to put down roots.
Dave Eggers and wife Vendela Vida wrote the original screenplay.
Gyllenhaal will play a bohemian college professor who is an old friend of the character played by Krasinski.
Collette dropped out of the film due to scheduling delays on the shoot, which recently got under way in Connecticut. Gyllenhaal begins filming her role next week.