Preheat your oven to 350°F (175°C) and grease a muffin tin or line it with cupcake liners.

In a large bowl, combine the rolled oats, baking powder, and salt. Stir gently to combine.

In a separate bowl, whisk together the milk, eggs, maple syrup (or honey), and vanilla extract until fully combined.

Pour the wet ingredients into the dry oat mixture and stir until everything is evenly mixed. Allow the mixture to sit for about 5 minutes.

Gently fold in your favorite mix-ins like berries or nuts.

Spoon the oatmeal mixture into the prepared muffin cups, filling them about 3/4 full.

Bake for 20-25 minutes or until the tops are golden and a toothpick inserted into the center comes out clean.

Let the oatmeal cups cool for a few minutes in the pan before transferring them to a wire rack. Serve warm or let them cool completely for storing.