1. Heat oven to 350 degrees. Combine all ingredients except pie filling and marshmallows in large bowl. Beat at low speed, scraping bowl often, until mixture resembles coarse crumbs. Reserve 1-1/2 C. crumb mixture for topping.
2. Press remaining crumb mixture into ungreased 13x9 baking pan. Bake for 12-15 minutes or until lightly browned on edges.
3. Gently spoon pie filling over hot partially baked crust; sprinkle with marshmallows. Sprinkle with reserved srumb mixture. Continue baking for 25-35 minutes or until lightly browned. Cut into bars.