An adjustable depth cover plate assembly includes a top plate and an adjustable sleeve to compensate for different spacing between the outer surface of a wall and the front side of an electrical box. The adjustable cover plate is positioned on the electrical box with the end of the sleeve abutting the electrical box. Mounting screws of an electrical wiring device pass through an opening in the top plate of the cover plate into the electrical box whereby the cover plate is captured between the wiring device and the electrical box. The length of the sleeve of the cover plate is adjustable by providing frangible score lines or telescoping members.