Preheat oven to 350°F; prepare a 12-cup muffin tin.
Pulse oats in a food processor into coarse flour. Mix with whole-wheat flour, baking powder, baking soda, salt, and cinnamon.
In another bowl, combine the whisked mashed bananas, yogurt, maple syrup, egg, and oil.
Fold wet and dry mixtures together just until combined; add chips or nuts if using.
Fill tins; bake 15 to 18 minutes until tops are lightly browned and a toothpick comes out mostly clean.
Cool five minutes in the tin, then transfer to a rack to prevent sogginess.