Heat oven to 350 degrees. Prepare cookie dough as directed and press into an ungreased 13x9 pan. Bake until golden brown for 16 to 18 minutes.
Spoon frosting into a microwave safe bowl. Microwave on high uncovered for 15 to 20 seconds. Stir frosting until its smooth. Reserve 1/4 C. Pour the remaining frosting over bars. Sprinkle the marshmallows and cereal over the frosting.
Bake until the marshmallows puff, usually takes from 3 to 5 minutes. Cool bars for 15 minutes. Drizzle the reserved frosting over the bars. Cool bars for 30 minutes. Cut into 6 rows by 4 rows.