HEAT oven to 350 degrees F. Spray a 13 x 9-inch glass baking pan with a no-stick cooking spray.
COMBINE shortening, sugar, brown sugar, egg and water in large bowl with electric mixer at medium speed, until well blended. Beat in 1/3 cup peanut butter and vanilla. In a separate bowl, combine flour, oats, baking soda and salt. Add gradually to creamed mixture at low speed. Beat until well blended. Spread into prepared baking pan.
Bake 20 to 25 minutes or until light brown and center is just set. Do not over-bake. Immediately sprinkle with chocolate chips. Let stand 5 minutes or until chips become shiny and soft. Spread to cover evenly. Cool slightly. Cut into bars, about 2 x 1 3/4-inches. Cool completely.
COMBINE powdered sugar, peanut butter and evaporated milk in small bowl, mixing until smooth. Drizzle over chocolate. Sprinkle with toffee bits, if desired.