Preheat the oven to 250°F (120°C) and line two large rimmed baking sheets with parchment paper.
Add the Rice Chex, Corn Chex, pretzels, Cheez-It crackers and peanuts to an extra-large mixing bowl, tossing briefly to distribute the smaller ingredients throughout the cereal.
4 cups (120 g) Rice Chex cereal, 4 cups (125 g) Corn Chex cereal, 1½ cups (60 g) pretzel twists, 1½ cups (93 g) Cheez-It crackers, 1 cup (145 g) roasted, salted peanuts
Whisk the BBQ sauce, melted butter, smoked paprika, garlic powder and onion powder in a small bowl until the butter and seasonings are fully incorporated into the sauce.
½ cup (120 ml) BBQ sauce, 2 tbsps (28 g) unsalted butter, 2 tsps (4 g) smoked paprika, 1 tsp (3 g) garlic powder, 1 tsp (2 g) onion powder
Pour the BBQ sauce mixture over the cereal mixture and toss thoroughly until the sauce is evenly distributed and there are no heavily coated or completely dry sections of cereal.
Divide the snack mix between the prepared baking sheets and spread it into an even layer, giving the moisture in the BBQ sauce enough exposed surface area to evaporate as the mixture bakes.
Bake for 30 to 40 minutes, stirring every 15 minutes, until the coating feels dry rather than wet or tacky.
Allow the BBQ Chex snack mix to cool completely on the baking sheets before serving or storing, as the coating will continue to firm as it cools.