Heat oven to 350°F. In large bowl, combine all base ingredients except marshmallows and chocolate chips; beat at low speed until crumbly. Press mixture firmly in bottom of ungreased 13x9-inch pan.
Bake at 350°F. for 12 to 15 minutes or until light golden brown.
Remove partially baked base from oven. Immediately sprinkle with marshmallows and 1 cup chocolate chips.
Return to oven; bake an additional 1 to 2 minutes or until marshmallows just begin to puff. Remove from oven; cool while preparing topping.
In large saucepan, combine all topping ingredients except cereal and peanuts. Cook over medium heat for 2 to 3 minutes or until margarine and chocolate chips are melted, stirring constantly. Stir in cereal and peanuts. Immediately spoon warm topping evenly over baked base; spread gently to cover. Refrigerate 1 hour or until firm. Cut into bars.