Abstract: The present invention is directed to an adjustable electrical outlet box assembly comprising an outlet box, an electrical outlet assembly, and an adaptor. The adaptor is located between the box and the outlet assembly and is positioned at least partially within the box. The adaptor includes opposing mounting flanges and opposing outlet assembly support tabs that are displaced from the mounting flanges. The adaptor may be adjusted to different heights, relative to the outlet box, to accommodate different thicknesses for different floor or wall covering materials. Due to the offset between the adaptor mounting flanges and the outlet support tabs, the outer surfaces of the outlet assembly will lie generally in the same plane as, or slightly recessed from the plane of the mounting flanges. The resulting outlet box installation can be used with a flush mounted cover plate which protects and secures the electrical outlet assembly.