HEAT oven to 375°F.
COMBINE first 5 ingredients in large bowl. Whisk peanut butter and milk in medium bowl until blended; stir in bananas, egg, oil and vanilla. Add banana mixture to dry ingredients; stir just until moistened.
SPOON into 12 muffin cups sprayed with cooking spray.
BAKE 18 to 20 min. or until toothpick inserted in centres comes out clean. Cool in pans 10 min. before removing from pan to serve.
serving size = 1 muffin (69 g)