Spray a 9x5 inch glass loaf pan with non-stick spray. Add vegetables in desired quantities. Season with salt and pepper. Pour in the egg whites. Microwave for 3 minutes on High. Remove from the microwave and stir to release cooked bits from the edges. Microwave for 3 minutes more. If the omelet is still runny on top, slice it into chunks and flip them over in the loaf pan. Microwave an additional 30 seconds. Season with additional salt and pepper to taste.