Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or lightly grease it.
In a large bowl, mash the bananas well. Whisk in the eggs, Greek yogurt, maple syrup, and vanilla extract.
Add protein powder, oat flour, baking soda, cinnamon, and salt. Stir until just combined.
Gently fold in the blueberries. Don’t overmix.
Divide batter evenly into 10 muffin cups, filling each about ¾ full.
Bake for 18–22 minutes, or until the tops are golden and a toothpick inserted comes out clean.
Let muffins cool in the pan for 5 minutes, then transfer to a wire rack to cool fully.