Pour the oyster crackers into a gallon-sized zip-top bag.

In a small bowl, combine the ranch dressing mix and garlic powder. Add the mixture and vegetable oil to the bag. Close the bag securely and shake gently to coat the crackers evenly. Be careful not to break the crackers while shaking.

Set the bag aside to rest for 30 minutes, allowing the crackers to soak in the oil and seasoning. Shake the bag gently again halfway through the resting time for even coating.

Preheat the oven to 250°F.

Spread the seasoned crackers in an even layer on two baking sheets. Bake at 250°F for 20 minutes. Halfway through baking, toss the crackers gently to ensure even seasoning and browning.

Cool the crackers completely to room temperature before serving.