Prep your pan: Heat the oven to 350°F (175°C).
Line a 12-cup muffin tin with liners or lightly grease it.
Mash the bananas: In a large bowl, mash the bananas until mostly smooth. A few small lumps are fine.
Whisk in wet ingredients: Add eggs, yogurt (or applesauce), maple syrup (or honey), vanilla, and oil. Whisk until well combined.
Combine dry ingredients: In a separate bowl, stir together oats, whole wheat flour, baking soda, baking powder, salt, and cinnamon.
Bring it together: Add the dry ingredients to the wet ingredients.
Stir with a spatula until just combined. Do not overmix.
Fold in extras: If using chocolate chips, nuts, or berries, gently fold them in now.
Fill the cups: Divide the batter evenly among the muffin cups. They should be almost full for nice domed tops.
Bake: Bake for 17–22 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Cool: Let the muffins rest in the pan for 5 minutes.
Transfer to a wire rack to cool completely. This helps set the crumb.
Enjoy: Eat warm or at room temp. Add a smear of almond butter if you want a little extra richness.