Mix brown sugar, butter and shortening in a large bowl. Stir in 1 ¾ cups flour, oats, salt and baking soda. Reserve 2 cups for topping. Press remaining mixture in an un-greased 13x9 inch pan. Toss apples and 3 tablespoons flour and spread over crust.
Heat caramels over low heat, stirring occasionally until melted, pour evenly over apples. Sprinkle with reserved oat mixture, press lightly.
Bake 25 to 30 minutes or until topping is golden brown and apples are tender. Cut into bars while warm. Store bars in an air tight container in the refrigerator.