Preheat the oven to 375 degrees F (190 degrees C). Line a 9x9-inch baking pan with parchment paper.
Stir together rolled oats, baking powder, cinnamon, and salt in a bowl; set aside.
Mash bananas in a large bowl until smooth. Whisk in milk, eggs, maple syrup, brown sugar, and vanilla extract until well combined.
Add oat mixture to banana mixture and stir until evenly blended. Pour batter into the prepared pan.
Bake in the preheated oven until golden brown and set, 35 to 40 minutes.
Transfer the pan to a wire rack and cool completely, about 30 minutes.
Cut into 9 bars. Serve and enjoy!
