Preheat the oven to 375ºF. Line a muffin pan with cooking spray or paper liners. Set aside.
To prepare the crumble topping, combine all ingredients in a medium bowl with a fork. Set aside.
In a medium sized bowl, combine flour, oats, baking powder, baking soda, and salt.
In a large bowl, beat the eggs and sugar. Add the milk, applesauce, vanilla, and banana. Combine but do not over mix. Add the dry ingredients and stir until just blended. Gently fold in the chocolate chips.
Divide batter evenly between prepared muffin cups. Top with the crumble topping, pressing down gently to adhere it to the batter. Bake 25-30 minutes or until golden brown.