Preheat your oven to 350°F (175°C) and prepare your muffin tin.
In a large mixing bowl, combine the rolled oats, baking powder, salt, and ground cinnamon.
In another bowl, whisk together the mashed bananas, eggs, milk, maple syrup, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and stir gently until just combined. Fold in the blueberries and nuts if using.
Divide the mixture evenly among the muffin cups, filling each about 3/4 full.
Bake for 20-25 minutes until golden brown and a toothpick comes out clean.
Allow to cool in the pan for a few minutes before transferring to a wire rack to cool completely.