Prep the ingredients per the instructions above.
Preheat the oven to 375°F (190°C). Line or lightly grease a muffin tin.
Mash the banana in a medium bowl until mostly smooth. Whisk in the egg, brown sugar, melted butter, milk, and vanilla until well combined. Stir in the rolled oats and let the mixture rest for 1 minute so the oats can soften. Add the flour, baking powder, baking soda, and salt. Fold gently until just combined. Fold in the chopped nuts.
Spoon the batter evenly into the muffin cups.
Bake for 18 to 20 minutes or until a toothpick inserted in the center comes out clean. Allow the muffins to cool slightly.
Brew and prepare the coffee to your liking.
Serve the oatmeal banana nut muffins with fruit and coffee. Enjoy your breakfast.