Preheat your oven to 375°F (190°C) and line a 12-cup muffin pan with paper liners.

In a large mixing bowl, whisk together all-purpose flour, old fashioned rolled oats, granulated sugar, baking powder, baking soda, ground cinnamon, and salt.

In a separate medium bowl, whisk the milk, vegetable oil, eggs, and vanilla extract until smooth.

Gently stir the mashed ripe banana into the wet mixture.

Pour the wet mixture into the dry mixture and stir gently until just combined.

If using, fold in the chocolate chips.

Using an ice cream scoop, divide the batter evenly among the muffin cups.

Bake for 18 to 22 minutes, or until the tops are golden brown and a toothpick inserted into the center comes out clean.

Allow the muffins to cool in the pan for a few minutes before transferring to a wire rack to cool completely.