The two actors are interested in Richard Curtis's (The Boat That Rocked, Love Actually) foray into science fiction, reports Variety.
First announced earlier this year, About Time is a low-budget project based on Curtis's own script.
The director previously helmed an episode of Doctor Who, 'Vincent and the Doctor'.
Actress and singer Deschanel is best known for her roles in films including Yes Man and 500 Days of Summer, and her current starring role in the television show New Girl.
Gleeson appeared as Bill Weasley in Harry Potter and the Deathly Hallows and played Bob Geldof in BBC Two's dramatization of Live Aid When Harvey Met Bob.
He will next be seen in Anna Karenina and Dredd, both of which are due for release this year.
Curtis most recently worked as co-writer on the script for Steven Spielberg's War Horse.