In large bowl, combine oats, flour, brown sugar, baking soda and salt; blend in margarine. Press in greased 9x13" baking pan. Bake in a preheated 350 degree oven 10 minutes. Sprinkle with chocolate chunks and pecans; pour caramel over top. Bake 20 minutes longer. Cool 1 hour at room temperature. Refrigerate, uncovered, until firm. Cut into bars.