A mounting adapter for use with E-track modular cargo track comprises a face plate and a jaw member. The jaw member comprises a generally cuboid body with two steps in the front face near each end and a bevel in the back face at each end. The steps and bevel cooperate to enable the jaw member to be inserted through the rectangular opening of the E-track into the narrow confines between the web of the E-track and the side or floor of the cargo bed. Once inserted, the steps center the jaw member vertically within the rectangular opening so that the face plate can be attached without the jaw member dropping into the space behind the E-track. The raised portions of the jaws include female threads adapted to receive a threaded fastener for fastening an object to the E-track while simultaneously capturing the E-track between the jaw and the face plate.