Heat oven to 400°F. Line twelve medium muffin cups with paper baking cups or spray bottoms only with cooking spray. In large bowl, combine flour, oats, sugar, nuts, if desired, baking powder and baking soda; mix well. In medium bowl, combine bananas, margarine, milk and egg whites; blend well. Add to dry Ingredients all at once; stir just until dry ingredients are moistened. (Do not overmix.) Fill muffin cups almost full. Bake 17 to 19 minutes or until golden brown. Cool muffins in pan on wire rack 5 minutes. Remove from pan. Serve warm.