Preheat oven to 400 degrees F. Line 12 medium muffin cups with paper baking cups, or spray bottoms only with cooking spray.
In large bowl, combine flour, oats, sugar, baking powder and baking soda; mix well. In separate bowl, combine bananas, butter, milk and egg whites; blend well. Add to dry ingredients all at once, and stir just until dry ingredients are moistened (do not over mix).
Divide batter evenly between the 12 muffin cups. Bake 14 to 18 minutes, or until golden brown. Cool muffins in pan on wire rack for 5 minutes. Remove from pan and serve warm.