Preheat your oven to 250 degrees Fahrenheit and line 2 large baking sheets with non-stick aluminum foil or parchment paper. Set aside.
Melt the butter either in a small saucepan over low heat or in a microwave-safe bowl. When the butter is completely melted, stir in the ranch seasoning mix, dill weed, garlic powder, onion powder, and ground black pepper.
Add the oyster crackers to a large mixing bowl and pour the butter mixture over the crackers. Gently stir with a rubber spatula until all the crackers are coated with the butter mixture.
Spread the crackers in a single layer on the baking sheets. Bake for 15-20 minutes or until the crackers begin to turn light golden brown, stirring once halfway through baking.
Sprinkle the crackers evenly with the grated Parmesan cheese immediately upon removing from the oven.
Allow the crackers to cool before serving.
