In large microwavable bowl, mix cereals, pretzels and peanuts.
In 2-cup microwavable measuring cup, microwave butter on High about 40 seconds or until melted. Stir in remaining ingredients. Pour over cereal mixture; stir until evenly coated.
Microwave uncovered on High 4 to 5 minutes, stirring every 2 minutes, until mixture just begins to brown. Spread on paper towels to cool. Store in airtight container.