In a large bowl, cream the butter, sugars and peanut butter until light and fluffy. Beat in egg and vanilla. Combine the flour, oats, baking soda and salt; gradually beat into creamed mixture and mix well. Spread into a greased 13x9-in. baking pan. Sprinkle with chocolate chips. , Bake at 350° for 20-25 minutes or until lightly browned. Cool on a wire rack for 10 minutes. , Combine icing ingredients; drizzle over the top. Cool completely. Cut into bars.