Preheat oven to 350 degrees. Grease a 13x9 pan.
In a large bowl, combine the first four ingredients until well blended. Press half of dough into a pan, reserve the rest for the topping.
In a heavy saucepan (or in the microwave), melt marshmallows until smooth. Combine dry pudding mix and mashed bananas, add in melted marshmallows. Spread evenly over dough in pan.
Crumble remaining dough over filling. Bake 20 to 25 minutes or until a light golden brown (mine took 30 minutes). Cool.