In a small bowl, whisk together the flour, oats, brown sugar, sugar, and cinnamon. Pour in the melted butter, and mix until completely combined. Set aside.
Make the Muffins
Preheat the oven to 350° F. Spray a muffin tin lightly with non-stick spray. Set aside.
In a large bowl, whisk together the flour, baking soda, baking powder, salt, cinnamon, and pumpkin pie spice.
In a separate bowl, whisk together the melted butter, sugar, eggs, vanilla, mashed banana, and pumpkin puree. Pour this into the dry ingredients and mix just until there are no streaks of flour left.
Scoop batter into prepared muffin pan, filling each muffin ¾ of the way full. Sprinkle the oat streusel over the tops of each muffin.
Bake for 17-23 minutes or until a toothpick comes out clean. Let muffins cool in the muffin tin for 3-5 minutes. Remove them from the pan and let them cool completely on a cooling rack.
Notes
Spoon and level your flour- I always recommend spooning and leveling your flour when baking or using a kitchen scale to measure your flour in grams.
Overmixing the batter - to make sure your muffins stay soft and don’t come out dry, stop mixing the batter as soon as there are no more streaks of flour. Overmixing it will cause dense muffins!
No Streusel - if you don’t want to add the streusel then feel free to leave that out!
Pumpkin Puree - make sure you are using pumpkin puree and not canned pumpkin pie filling!