Preheat oven to 350°F. Mix flour, oats, sugar, baking soda, salt and spices in large bowl. Add butter; stir until mixture is well blended and forms coarse crumbs. Reserve 1/2 (about 2 1/4 cups) for the topping. Add pumpkin and vanilla to remaining mixture in bowl; stir until well blended. Press evenly into bottom of greased foil-lined 13x9-inch baking pan. Set aside.
Microwave caramels and milk in medium microwavable bowl on HIGH 2 to 3 minutes or until caramels are completely melted, stirring after every minute. Let stand 1 minute. Pour over pumpkin mixture in pan, spreading to within 1/2-inch of edges. Sprinkle with reserved crumb mixture.
Bake 30 to 35 minutes or until light golden brown. Cool in pan on wire rack. Lift from pan. Cut into bars.