Preheat oven to 375°. Spray a 6-hole Texas Muffin pan with non-stick cooking spray. Set aside.
In a large bowl, combine all of the dry ingredients.
In a separate bowl, mix together the eggs, buttermilk, bananas, pumpkin, butter and vanilla extract.
Add the dry ingredients into the wet ingredients and stir until just combined. Set aside while making topping.
For streusel topping, combine oats, brown sugar and cinnamon. Cut butter into dry ingredients until crumbly.
Fill muffin cups ¾ full, sprinkle with streusel topping and bake on center rack of the oven for approx. 30 minutes or until a toothpick inserted into a muffin comes out clean. Cool in pan for 5 minutes, then remove from pan to a cooling rack to finish cooling.