In his early years, Birnbaum served as producer under his Caravan label for several Disney films, such as Angels in the Outfield, Heavyweights, The Big Green, RocketMan, as well as films distributed by Touchstone Pictures (like I Love Trouble and Metro) and Hollywood Pictures (such as Celtic Pride, Powder, and Holy Man). In 1998, Birnbaum left Caravan to co-found Spyglass Entertainment. In 1999, however, shortly after the release of Inspector Gadget, Caravan closed its doors.
Under the Spyglass label, Birnbaum served as executive producer for films such as The Pacifier and Eight Below. He also produced Touchstone films, like Instinct, Shanghai Noon, and The Hitchhiker's Guide to the Galaxy and Hollywood Pictures films, such as Stay Alive and The Invisible. He even produced the 2007 Miramax film, The Lookout.