Preheat oven to 350 degrees. Line a 12-cup muffin pan with muffin cups.
Place the oats in a food processor and pulse until it forms an oat flour.
Add in the whole wheat flour, cinnamon and salt, and pulse again. Add in the pumpkin, banana, milk, vanilla extract, maple syrup, and baking powder. Pulse again just until combined.
Remove the bowl from the processor bottom, and remove the blade from the bowl. Slowly add in the chopped apple and mix together with a spoon.
Evenly spoon the batter into the muffin cups.
Bake for 20 minutes, or until the center of the muffins comes out clean with a toothpick.
Allow to slightly cool, then enjoy!