The present invention provides a barbecue grill assembly with a grill body having a firebox and a cover and a burner element. The firebox is supported on a frame structure having a first frame member assembly and a second frame member assembly. The frame assemblies are secured together by combination of at least one cross member secured to the upper portion and being secured to the firebox at a lower region, without the need for additional cross members at the lower region. The invention further provides a frame with pivoting shelves secured to the frame, adapted to move from a use position to a storage position within the grill cooking chamber. The present invention further provides a frame assembly having a lateral slot for receiving and supporting a heat shield positioned below the firebox.