Preheat the oven to 350°F. Lightly spray a muffin pan with cooking spray and set aside.
In a large bowl, mix together the flour, brown sugar, baking soda, baking powder, nutmeg, cinnamon and salt. Add in the oats and raisins.
Fold in the oil, egg, milk, carrots and banana until fully combined.
Divide the batter evenly into the cavities of the muffin pan and bake in the preheated oven for 25 minutes. Allow to cool for 5 minutes in the pan, then transfer to wire racks to cool completely.
Notes
I use avocado oil in this recipe, but any neutral oil works.