Preheat oven to 350 degrees F. Line large baking sheet with unbleached parchment paper or silicone baking mat, and spray with cooking spray.
In a medium bowl, mash bananas with a fork. Add whey protein powder, oats and peanut butter. Stir well to combine, batter's consistency will be runny. Add chocolate chips and give a few more stirs.
Spoon mixture onto prepared baking sheet (cookies don't spread, so shape them now) and bake for 12-14 minutes (depending on size).
Cool on a cooling rack for 5 minutes.
