Preheat oven to 350 degrees F. Grease an 8×8-inch baking dish with nonstick cooking spray and set aside.
In a large bowl, combine the oats, cocoa, baking powder, and salt. Set aside.
In a medium bowl, combine mashed bananas, milk, peanut butter, eggs, maple syrup, and vanilla extract. Whisk until combined.
Add the liquid ingredients to the oat mixture and stir until combined. Stir in ¼ cup chocolate chips.
Pour the oatmeal mixture into prepared pan and sprinkle with additional chocolate chips. Bake for 35 minutes or until oatmeal is set.
Remove from the oven and cool for 5 minutes. Cut into squares and serve with a drizzle of peanut butter and a sprinkle of flaky sea salt, if desired.
