Meanwhile, heat oven to 350°F. In medium bowl, combine flour, 1/2 cup pecans and 1/4 cup brown sugar; mix well. With pastry blender or fork, cut in 1/2 cup butter until mixture resembles coarse crumbs. Press in bottom of ungreased 13x9-inch pan. Bake at 350°F. for 10 to 14 minutes or until light golden brown. Cool 30 minutes.