Prep:
Preheat the oven to 350F and line a baking sheet with parchment paper.
Make the batter:
In a medium bowl, mash the bananas with a fork. Add the applesauce and vanilla, stir to combine. Mix in the old-fashioned oats and thoroughly combine until you have a thick batter.
Gently fold in the blueberries.
Make the cookies:
Using a cookie scooper or large tablespoon, scoop the batter onto the lined baking sheet, gently press the dough with the back of the scoop or spoon, to flatten the cookies
Transfer the baking sheet into the preheated oven and bake for 20 to 25 minutes or until the cookies are a light, golden brown.