Preheat oven to 350 degrees F.
Spray muffin pan with cooking spray. Set aside.
In a large bowl, combine flours, oats, oat bran, flax seeds, baking soda, baking powder, and salt.
Mix well.
In medium bowl, combine mashed bananas, yogurt, egg, and vanilla extract.
Pour banana mixture into flour mixture and stir well with wooden spoon, until just combined.
Fill each muffin tin about ⅓ of the way.
Spoon in 1-2 teaspoon of peanut butter, according to your preference.
Fill each muffin tin with remaining batter, about ¾ of the way to the top.
Bake in preheated oven for 15 minutes, until tops spring back.
Let cool in muffin pan 10 minutes, then remove from muffin pan and cool completely.
Enjoy!