Combine oats, oat bran, egg whites and salt until oats are evenly coated; set aside. Saute mushrooms, green pepper and onions in margarine over medium-high heat 2 to 3 minutes or until vegetables are crisp-tender. Add oat mixture; cook over medium heat about 5 to 6 minutes, stirring constantly, or until oats are dry, separated and lightly browned. Add broth; continue cooking 2 to 3 minutes or until liquid is absorbed. Stir in tomato; serve immediately.