Slice beef into ¼ inch wide strips. Saute in 2 tbsp. margarine and 1 tbsp. oil in large skillet. Place in baking dish. Sprinkle with salt, pepper, sage and cumin; toss lightly. Saute mushrooms in remaining margarine and oil in skillet for 2 minutes. Add to casserole. Stir green peppers, garlic and onion into pan drippings. Saute for 2 minutes. Add to casserole. Arrange tomatoes on top. Combine remaining ingredients in skillet. Heat to boiling point, stirring constantly. Pour over beef mixture; toss lightly. Bake, covered, in 350 degree oven for 30 minutes.