Preheat your oven to 375°F (190°C). Line a muffin tin with paper liners.
In a bowl, combine the oats and milk. Let it sit for 10 minutes.
In another bowl, whisk together the flour, brown sugar, baking powder, baking soda, and salt.
Add the oil, vanilla extract, and egg to the oat mixture. Mix well.
Gradually add the dry ingredients to the wet ingredients. Stir until just combined.
Fold in the chocolate chips.
Divide the batter evenly among the muffin cups.
Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean.
Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.