Heat oven to 400°F. Spray bottoms only of 12 muffin cups with nonstick cooking spray. In large bowl, combine flour, oats, 1/4 cup sugar, baking powder, 1/2 teaspoon cinnamon and nutmeg; mix well.
In small bowl, combine bananas, buttermilk, oil and egg; beat well. Add to flour mixture; stir just until dry ingredients are moistened. Fill sprayed muffin cups 3/4 full.
In another small bowl, combine topping ingredients; mix well. Sprinkle evenly over batter in cups.
Bake at 400°F. for 15 to 18 minutes or until toothpick inserted in center comes out clean. Cool 1 minute; remove from pan. Serve warm.