An adjustable bracket assembly having a pair of longitudinally spaced tab members, each including a notched portion in mirrored image to the other for insertion in spaced slots of a support member. One of the tab members includes a threaded stud and the other tab member includes a sleeve through which the stud passes. A nut, threadly mounted on the threaded stud adjacent the free end of the sleeve, is rotatable to adjust the spacing between the tab members to correspond to the spacing between a pair of slots in the support member. The notched portions of each tab member includes a tapered surface for enabling the tab members to be secured to support members having varying wall thicknesses.