Preheat your oven to 350°F (175°C). This ensures your muffins bake evenly and rise perfectly.
If you’re using muffin liners, place them in the muffin tin. Alternatively, lightly grease the muffin pan with cooking spray or melted butter.
In a large mixing bowl, whisk together the whole wheat flour, oats, brown sugar, baking powder, and baking soda until well combined.
In another bowl, mix together the mashed bananas, melted butter, nonfat milk, and egg whites (or egg). Whisk until smooth.
Pour the wet mixture into the dry ingredients. Stir gently until just combined. Be careful not to overmix; a few lumps are okay.
Scoop the batter into the prepared muffin tin, filling each cup about ¾ full. This will allow room for the muffins to rise.
Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Once baked, remove the muffins from the oven and let them cool in the pan for about 5 minutes. Then transfer them to a wire rack to cool completely before serving.
