Abstract: The present invention involves a foldable bay window for mobile living quarters, such as recreational vehicles, is movable between an extended position, in which the bay window projects from a wall of the unit to a folded position, in which the components of the bay window assembly are substantially flat against the outer wall of the unit. The bay window assembly includes a pair of side panes which are slidably and pivotally mounted on horizontally extending tracks on the wall of the unit, and a center pane connecting the side panes. A bottom panel is pivotally connected to the wall or center pane and is constrained for movement along vertical tracks, to thereby force the panes into the folded position as the bottom panel is moved from a substantially horizontal position to a substantially vertical position. As the panes are folded against the wall of the vehicle, a hinged roof panel drops into a substantially vertical position.