Preheat your oven to 300 degrees F.
In a very large bowl, combine the pretzels, Goldfish crackers, Chex, and Cheerios cereal.
Place the butter in a microwave-safe bowl and heat in 15-second increments until the butter is completely melted.
Drizzle the melted butter over the mix in the large bowl and stir to combine.
Add the ranch dressing seasoning to the bowl and stir well, making sure that everything is coated with the seasoning.
Prepare 2 parchment-lined rimmed baking sheets and spread the mixture out evenly on the baking sheets.
Bake in the middle of the oven for 40-50 minutes, stirring the mixture halfway through. You want the mixture toasted golden brown; be careful not to let it burn. Check it after 30-35 minutes for doneness.
Remove from the oven and allow to cool completely. Then add the caramel corn and toss.
Store in an air-tight container.