Preheat oven to 25o degrees.
In a large bowl mix together cereals, pretzels and peanuts.
Put butter, mustard, honey, seasoned salt and onion powder in a microwavable bowl. Microwave on high 1-2 minutes or until butter is melted and mixture is hot. Stir. Pour over cereal mixture; stirring evenly to coat
Pour the snack mix on to two large rimmed baking sheets. Bake mix in preheated oven for 40 minutes. Stirring after 20 minutes.
Remove from oven and let cool. Store in airtight container.
