In a large bowl, combine the flour, oats, brown sugar and baking soda. Cut in butter until mixture resembles coarse crumbs. Set aside 2 cups for topping. Press remaining crumb mixture into a greased 15x10x1-in. baking pan. Bake at 350° for 8-10 minutes or until set.
In a microwave-safe bowl, heat frosting for 30-45 seconds or until softened; stir well. Spread over crust. Sprinkle with chocolate chips and pecans. Top with reserved crumb mixture.
Bake for 14-18 minutes or until frosting is bubbly and top is golden brown. Cool completely on a wire rack; cut into squares.