A hollow beam for incorporation in an automotive vehicle frame is useful as a transmission cross member extending between side rails of the automotive vehicle frame. The hollow beam has first and second U-shaped channels, each comprising a base wall and a pair of side walls extending transversely from the base wall. The channel members are made of a thermosetting polyester which is reinforced with glass fibers. The side walls of the second channel are received within the sidewalls of the first channel and adhered thereto with epoxy to form a rigid, relatively light weight beam. The beam has figure-8 shaped aluminum inserts proximate the ends thereof for attaching the beam to the side rails of the automotive vehicle frame.