Abstract: A waveguide structure for use in a microwave oven wherein a portion of the wall structure defining the oven cavity also forms a portion of the waveguide. The waveguide is formed of a plurality of wall members cooperatively defining a waveguide conduit for delivering microwave energy from a generator through an inlet opening in the oven cavity wall. The several wall members of the waveguide conduit are press-formed and secured together by mechanical fastening structure to provide high accuracy in the waveguide configuration. The conduit wall further includes a mounting flange secured to the cavity wall to provide further precise accurate association of the waveguide conduit with the cavity wall opening. An external paint coating on the cavity wall defines with a mounting flange of the waveguide conduit wall a capacitive seal therebetween.