Preheat the oven to 250°F and line a baking sheet with parchment paper.
In a small bowl, mix the dry ranch seasoning ingredients (everything but the butter) and set aside.
¼ cup buttermilk powder, ½ tbsp dried dill, ½ tbsp dried chives, ½ tbsp dried parsley, ½ tbsp onion powder, ½ tsp garlic powder, ¾ tsp pepper, ¼ to ½ tsp chipotle pepper powder, ½ tsp salt
Add Cheez-Its, pretzels, oyster crackers, and Chex cereal to a bowl. Gently mix in half of the melted butter and half of the ranch seasoning mix, then repeat with the rest of the butter and dry seasoning until all of the snack mix is well-coated.
3 cups corn Chex cereal, 1 cup pretzel twists, 2 cups Cheez-Its crackers, 1 cup oyster crackers, ¼ cup melted butter
Spread the seasoned snack mix on the baking sheet in an even layer. If your baking sheet is too small, you can use a 2nd one lined with parchment paper.
Bake for 15 minutes, then remove from the oven and toss well.
Bake for another 15 minutes, then toss again, and bake for a final 15 minutes. The snack mix should be just slightly toasted and the seasoning should stick on the snacks.
Let the ranch snack mix cool before eating (they will crisp up as they cool).