Preheat your oven to 350°F (175°C).
Line your muffin tin with parchment paper liners or grease it with butter or non-stick spray.
In a medium bowl, whisk together the all-purpose flour, old-fashioned oatmeal, baking soda, and salt until well combined. Set aside.
In a large mixing bowl, cream together the softened butter, light brown sugar, and granulated sugar until light and fluffy, about 2-3 minutes.
Add the eggs one at a time, mixing well after each addition. Stir in the mashed banana and vanilla extract until fully incorporated.
Gradually add the dry ingredient mixture to the wet ingredients, stirring gently until just combined.
Gently fold in the chocolate chips until evenly distributed.
Fill each muffin cup about 3/4 full with batter. Bake for 18-22 minutes, or until a toothpick comes out clean.
Remove from the oven and cool in the pan for about 5 minutes before transferring to a wire rack to cool completely.
