- Preheat the oven to 350 degrees F (175 degrees C). Grease a 9×13 inch baking pan.
- In a medium bowl, mix together the butter, brown sugar and egg until smooth. Stir in applesauce. Combine the flour, baking soda, salt and pumpkin pie spice; stir into the applesauce mixture until well blended. Spread evenly into the prepared pan.
- Bake for 25 minutes in the preheated oven, or until edges are golden. Cool in the pan over a wire rack.
- In a small bowl, mix together the confectioners’ sugar and margarine. Stir in vanilla and milk until smooth. Spread over cooled bars before cutting into squares.