1. In a large bowl, cream 1 cup peanut butter, butter, brown sugar and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in applesauce and vanilla. Combine the flour, oats and baking soda; gradually add to creamed mixture and mix well (batter will be thick).
2. Spread into a 15-in. x 10-in. x 1-in. baking pan coated with cooking spray. Bake at 350° for 18-22 minutes or until lightly browned. Cool on a wire rack for 10 minutes; spread with remaining peanut butter. Cool to room temperature, then refrigerate for 30 minutes.
3. In a large bowl, beat frosting ingredients until light and fluffy. Spread over the peanut butter layer. Cut into bars. Yield: 3 dozen.