1Heat oven to 350°F. Make cookie dough as directed on pouch. Press dough into ungreased 13x9-inch pan.
2Bake 16 to 18 minutes or until golden brown around edges.
3Spoon frosting into microwavable bowl. Microwave uncovered on High 15 to 20 seconds; stir frosting until smooth. Reserve 1/4 cup. Pour remaining frosting over warm bars. Sprinkle marshmallows and cereal over frosting.
4Bake 3 to 5 minutes longer or until marshmallows are puffed. Cool 15 minutes. Drizzle reserved frosting over bars. Cool completely, about 30 minutes. For bars, cut into 6 rows by 4 rows.