Sheridan, 19, will play Wade Watts, a poor orphan from the "stacks" surrounding metropolitan Oklahoma who joins the Oasis, reported Variety online.
"Me and Earl and the Dying Girl" star Olivia Cooke has already been cast in the female lead, and Ben Mendelsohn is also on board for a role.
The Warner Bros, Village Roadshow and DreamWorks release is based on the buzzy Ernest Cline book of the same name.
Spielberg, Donald De Line, Dan Farah and Kristie Macosko Krieger will produce, with Bruce Berman serving as exec producer.