Preheat your oven to 180°C (350°F) and line a muffin tin with paper liners. Gather all your ingredients so they’re ready to go.
Peel and mash the bananas in a large mixing bowl with a fork until smooth, releasing a sweet, fragrant aroma.
Add the rolled oats, flour, baking powder, baking soda, salt, and brown sugar directly into the mashed bananas. Briefly stir with the whisk to combine everything into a thick, lumpy batter.
Pour in the melted oil and vanilla extract, then gently fold everything together just until combined. The batter should be a bit lumpy with visible oats and banana chunks.
If using chocolate chips or nuts, fold them into the batter now for extra texture and flavor.
Spoon the batter into your prepared muffin tin, filling each cup about three-quarters full. Gently press down to even out the tops.
Bake in the oven for about 20–25 minutes, or until the muffins turn a warm golden brown and a toothpick inserted in the center comes out clean. You’ll hear a slight crackle on top as they bake.
Remove the muffins from the oven and let them cool in the tin for 5 minutes. The aroma of toasted oats and caramelized bananas will fill the kitchen.
Transfer the muffins to a wire rack and allow them to cool slightly before serving. The tops should be slightly cracked and the muffins feel firm but tender to the touch.
Enjoy warm or at room temperature, ideally within a day for the best flavor and texture. These muffins are perfect for a cozy breakfast or a quick snack!