Preheat oven to 350 degrees. In a large bowl, combine all the crust ingredients, except for marshmallows. Press into the bottom of an ungreased 9x13 pan and bake 12-15 minutes.
Remove from the oven and immediately sprinkle marshmallows over the crust. Bake an additional 1-2 minutes longer.
While the base is cooling, prepare the topping. In a large saucepan, heat corn syrup, butter, vanilla and peanut butter chips until smooth, stirring constantly. Remove from heat, stir in cereal and nuts. Immediately spoon over the marshmallow crust and spread to cover.