Preheat oven to 375 degrees. Line a muffin pan(s) with liners or spray with nonstick cooking spray.
In a medium mixing bowl, whisk together flour, oats, baking powder, and salt until combined. Set aside.
In a separate bowl, whisk together the milk, vegetable oil, brown sugar, eggs, and vanilla.
Slowly add the dry ingredients to the wet ingredients one cup at a time, stirring between each addition.
Fold in the chocolate chips.
Spoon the batter into the muffin pan, filling each cup 2/3 of the way full.
Bake in the preheated oven for 22 to 25 minutes. The muffins are done when a toothpick inserted in the center comes out clean.
Allow the muffins to cool in the pan for 5 minutes, then remove to a wire cooling rack to cool completely.