Preheat oven to 350°F. Grease and flour an 8.5 x 4.5-inch bread pan; set aside.
Peel bananas and beat with electric hand mixers in a large bowl until smooth and to applesauce consistency. Measure out 1 cup and level off the top.
Add a heaping ⅓ cup oats to a high-powered blender and blend until fine. Measure out a leveled ⅓ cup.
Make sure all wet ingredients are at room temperature to prevent clumping. In a large bowl, whisk together mashed banana, Greek yogurt, egg, vanilla, melted (but not hot) coconut oil, honey, and brown sugar until smooth.
Add baking soda, salt, cinnamon, cornstarch, and oat flour right on top of the wet mixture and whisk until combined. Add in the flour, then switch to electric hand mixers and beat just until combined—don’t overmix.
Pour batter into prepared pan. For a sweet crust, sprinkle 2 tablespoons brown sugar on top (optional). Bake for 45–60 minutes, or until a fork inserted in the center comes out clean or the bread pulls away from the edges. Tent with foil if the top browns too quickly.
Video
Notes
Storage: Store in an airtight container in the fridge for up to 3 days. Warm slices in the microwave for 5–10 seconds. For longer storage, wrap individual slices tightly and freeze.