Abstract: A high-frequency dielectric oven uses a plurality of oscillating circuits, which are caused to operate in a predetermined phase relationship, to produce a higher voltage distribution within a load capacitor, thus permitting an increase in the space between the electrode plates of the load capacitor to enable use of the oven for heating commercial quantitites of foodstuff. The generated electric field has a distribution which minimizes the number of nodes of a standing wave, thus reducing the occurrences of cold spots in the heating cavity. A plurality of tray levels are provided, each level having a separate pair of electrodes generating the electric field therefor. The electrodes may be shaped to provide direct support for the trays. Power transferred to the foodstuff is controlled by a variable air gap capacitor and the power tube operates at a substantially constant power level, irrespective of the power being transferred to the foodstuff.