Preheat oven to 250°.
Melt the butter either in the microwave or on the stove and pour over oyster crackers in a large bowl, stirring to coat evenly.
Combine the sugar and cinnamon in another small bowl, mixing well.
Pour the cinnamon sugar mixture over the butter-coated crackers and stir until they are evenly coated.
Bake for 30 minutes, until crispy.
Let cool completely before eating or storing them.
