Preheat the oven to 350 degrees F (175 degrees C). Line a baking sheet with parchment paper.
Mix together mashed bananas, milk, egg, honey, and vanilla in a bowl. Stir in oats, cinnamon, baking powder, and salt until well combined. Add more oats if the batter is too runny.
Spoon mounds of batter a few inches apart onto the prepared baking sheet.
Bake in the preheated oven until the tops look dry and edges are golden, about 15 minutes.