Steam oysters outside on the grill to cook them in just a few minutes. Fresh oysters contain water that when heated turns to steam and quickly cooks and opens the oysters. Steaming the oysters in their own natural juices retains the flavors of the waters where they were harvested. The entire steaming process must be closely monitored to avoid contamination and overcooking. Turn your grill into an oyster steam chamber to cook a large quantity of shellfish fast.
Place the oysters in a large tub. Rub their shells under cold running water with gloved hands. Even oysters that are sold as precleaned should be washed using this method.
Pour all of the rinse water out of the tub. Slide the tub of oysters into a refrigerator that is running between 35 and 40 degrees Fahrenheit.
Pour half the bag of briquettes into an outside charcoal grill. Light the pile with wooden matches.
Cover the coals with the grill grate, and allow them to burn until they have mostly turned gray. This takes between 15 and 30 minutes, depending on the charcoal and the grill.
Test the temperature of the heat source by holding your hand an inch above the grill grate. The coals are hot when it is painful to keep your hand in position for more than three or four seconds.
Remove the oysters from the refrigerator. Give them one final rinse in cold running water so they are wet for the grill.
Crowd the grill grate with a single layer of fresh oysters. Leave just enough room at the sides of the grate to cover with the lid.
Lift the lid after four minutes. Use tongs to remove any oysters that have steamed open.
Replace the lid, and wait in one-minute intervals between checking for newly opened oysters. After eight minutes of steaming, discard any remaining oysters that do not open.
A gas grill can also be used to steam open fresh oysters outside, but it does not impart the smoky flavor of charcoal. Preheat the gas grill for 15 minutes. Test its heat with your hand an inch above the grill grate before loading the gas grill with oysters and closing the lid.
Oysters should always be used the same day or one day after you purchase them. Ask the seafood seller which oysters came in most recently in order to buy the freshest product.