Combine the rice, wheat, and corn Chex cereals, pretzels, and unsalted peanuts in a slow cooker. Set aside.
In a small bowl, whisk together the melted butter, soy sauce, BBQ sauce, garlic salt, and onion powder.
Pour the seasoned butter mixture over the cereal mixture and toss everything together until well combined.
Cover and cook on low for 2-1/2 hours or until cereal has lightly browned. Stir the mixture every 30 minutes to ensure nothing burns and to get an even color on the cereal.
Once the mix is done cooking, pour the Chex mix onto a sheet pan lined with parchment paper and spread it out evenly.
Allow it to cool completely before serving, about 30 minutes.
Notes
You can easily scale up this recipe to make a larger batch. Ensure you have a big enough slow cooker, or use multiple slow cookers if needed.
Allow the Chex Mix to cool completely before storing. Place leftovers in an airtight container or a sealed bag to prevent the cereal and pretzels from becoming stale. Store at room temperature for up to 3 weeks. For longer-term storage, you can freeze it for 4-6 months.