Marshmallow Krispie Bars

1 pkg p Chewy Brownie Mix
1 - 20oz pkg mini marshmallows
1 1/2 cup semi-sweet chocolate chips
1 cup creamy peanut butter
1 Tbs. margarine
1 1/2 cups Rice Krispies

Preheat oven to 350°F. Grease bottom of 9x13 pan.  Prepare brownies as on package and bake.  As soon as brownies come out of the oven, sprinke marshmallows on top, then bake 3 minutes more. Put chocolate chips, peanut butter and margarine in saucepan; cook until melted. Add Rice Krispies to chocolate/peanut butter mixture and blend well. Spread chocolate/peanut butter/krispie mixture over marshmallow layer.  Refrigerate until cooled, then cut into bars.