Until recently, heat has been the usual direct energy source for cooking. Microwave energy has become available through the use of electronic ovens. The development of plastic wraps that can be used in oven cookery led to a study of the effects of these on cooking losses and other characteristics of beef roasts cooked by microwave and by heat energy. Twenty‐four choice semitendinosus muscles were divided into anterior and posterior sections, and each was allocated to one of four cooking methods: conventional electric oven, meat uncovered; conventional oven, meat tied in modified polyester sleeve; microwave oven, meat uncovered; microwave oven, meat tied in polyester sleeve. A randomized incomplete block design was used and replicated 12 times. Cooking times were significantly less and cooking losses greater for roasts cooked by microwave than by conventional heating. Use of polyester wrap increased the cooking losses for both heating methods. The change in percent total solids with cooking was greater for roasts cooked electronically than for roasts cooked conventionally. Shear force was not affected by any of the four cooking methods. Penetrometer readings ranged from highest for uncovered roasts to lowest for covered roasts in the conventional oven. Of taste panel scores, only the scores for external color differed significantly.