Combine the two cereals into a large bowl; set aside.
In 1-quart microwavable bowl, microwave chocolate chips, peanut butter and butter uncovered on High 1 minute; stir. Microwave about 30 seconds longer or until mixture can be stirred smooth.
Stir in vanilla. Pour mixture over cereal, stirring until evenly coated.
Pour into 2 separate gallon resealable food-storage plastic bag. We love these bag holders for this task!
Add powdered sugar. Seal bag; shake until well coated.
Spread on waxed paper to cool. Store in airtight container in refrigerator.