Preheat the oven to 250°F. Combine the cereals, pretzels, Cheez-Its, peanuts, and pecans in a large roasting pan.
Melt the butter in a small saucepan over medium-low heat. Stir in the Worcestershire sauce, seasoned salt, garlic powder, and onion powder.
Pour the butter mixture over the ingredients in the roasting pan, and stir gently to coat.
Bake the party mix for 1 hour, stirring every 15 minutes, until the ingredients are lightly toasted. Let cool completely before storing in an airtight container or cellophane bags for gift giving.