A grab bar is attached to a wall of a shower enclosure with at least one anchor assembly. When installed, a grab bar mount flange covers the anchor assembly from view. The anchor assembly includes a flange collar with a collar bore and a jackscrew that is received within the collar bore. The flange collar is installed within an opening formed within the wall of the shower enclosure. A position of the jackscrew can be adjusted without having to remove the flange collar from the wall. Once properly adjusted, a fastener is inserted through the grab bar mount flange, flange collar, and jackscrew for securement to a wall structure behind the shower enclosure.