For cookie base and topping, beat together margarine and sugar until light and fluffy. Blend in egg and vanilla. Add combined flour, soda and salt; mix well. Stir in oatmeal. Press 2/3 of mixture onto bottom of greased 9 x 13 pan. Reserve remaining mixture for topping.
For filling melt together chocolate chips, sweetened condensed milk, margarine and salt in microwave until melted and smooth. Add vanilla. Spread evenly over base mixture. Sprinkle reserved cookie base and topping mixture evenly over chocolate layer. Bake in preheated oven.
