Preheat your oven to 350°F (175°C). Line a standard 12-cup muffin tin with paper liners or spray it generously with non-stick cooking spray. This ensures your muffins pop out easily without sticking to the sides.

In a large mixing bowl, peel the bananas and mash them thoroughly with a fork or a potato masher. You want a relatively smooth consistency with only a few small chunks remaining for the best texture.

Add the eggs, peanut butter, maple syrup, and vanilla extract to the mashed bananas. Whisk everything together until the mixture is well-combined and the peanut butter is fully integrated into the batter.

Stir in the rolled oats, protein powder, baking powder, cinnamon, and salt. Use a spatula to fold the ingredients together until just combined. If you are using chocolate chips or nuts, fold them in gently at the very end. Be careful not to overmix, as this can make the protein powder “tough.”

Divide the batter evenly among the 12 muffin cups. They should be about 3/4 full. Place the tin in the center rack of the oven and bake for 18 to 22 minutes. A toothpick inserted into the center should come out clean when they are finished.

Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack. Cooling them completely helps the structure set, making them easier to peel from the liners. Enjoy them warm or store them for later!