Abstract: A full bore set down tool assembly provides a housing attached to a packer in a wellbore and aligned with the production zone. A service tool of the tool assembly is attached to a tubing string extending to the surface and is adapted for selective, removable attachment to and positioning within the housing. The tool assembly defines a downstream flow path and a return flow path when the service tool is attached to the housing. A ball valve that is selectively shiftable from the surface opens and closes the return flow path to define a circulate position and a squeeze position. The housing, service tool, and ball valve also define a reverse position. The tool assembly facilitates gravel packing of the annulus between the wellbore casing and the service string including the tool assembly.