Preheat the oven to 250 F and spread the oyster crackers in a single layer across a large rimmed baking sheet.

Whisk the vegetable oil, ranch seasoning, garlic powder and cayenne together in a small bowl.

Pour the oil mixture over the crackers and toss with a spatula until every cracker is lightly glossed.

Bake for 20 minutes, stirring once halfway through, until the crackers smell toasted and feel dry rather than oily to the touch.

Cool completely on the sheet, about 15 minutes, before pouring into a serving bowl; they crisp further as they cool.