Preheat your oven to 350°F (175°C). This ensures that your oatmeal cups bake evenly.
Grease your muffin tin with a little coconut oil or use muffin liners for easy removal.
In a large mixing bowl, combine the milk, mashed bananas, nut butter, melted coconut oil, and vanilla extract. Whisk these ingredients together until well combined.
In another bowl, mix together the old-fashioned oats, baking powder, ground cinnamon, and salt. Stir to combine.
Add the dry ingredients to the wet mixture. Stir until just combined. Be careful not to overmix!
Gently fold in your chopped nuts, dried fruit, and mini chocolate chips. This is where you can really personalize your oatmeal cups!
Spoon the oatmeal mixture evenly into the prepared muffin tin. Fill each cup about 3/4 full.
Place your muffin tin in the preheated oven and bake for 25-30 minutes, or until the tops are golden and a toothpick inserted in the center comes out clean.
Allow the oatmeal cups to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely. Enjoy warm or store for later!