Melt Butter In A Medium Saucepan Over Medium Heat. Stir In Green Bell Pepper, Red Bell Pepper, Onion And Portobello Mushrooms. Cook Until Tender, About 5 Minutes. Stir Beef Into The Vegetable Mixture, And Cook Until Evenly Brown, 5 To 10 Minutes. Stir Egg Beaters Into The Mixture, And Cook 10 Minutes, Or Until Firm.