Preheat oven to 400 F. Peel pears and cut into bite-size pieces. Set aside. In a large bowl, combine remaining filling ingredients and fold in pears. Pour pear mixture into pie crust and bake at 400 F for 15 minutes Lower heat to 350 F and continue baking for 25 minutes more. Mix together topping ingredients. Remove pie from oven and sprinkle topping over filling. Raise heat to 375 F and bake until topping is brown.