Abstract: A microwave oven includes a relatively flat mode stirrer cavity mounted on the outside of one of the cooking cavity walls, sharing a common wall therewith. Disposed within the mode stirrer cavity is a rotating fan-like mode stirrer. A waveguide supplies 2450 MHz microwave energy to the mode stirrer cavity. Two aperture elements of generally slot configuration and oriented at right angles to each other in the common wall couple energy from the mode stirrer cavity into the cooking cavity. The configuration and relationship of the aperture elements promote uniformity of energy distribution and readily permit adjustment of the energy distribution by empirically adjusting the precise size and location of each aperture element. In one embodiment of the invention, two aperture elements overlap to form a single aperture of substantially cruciform configuration.