Trim any fat or membranes off the top side of the oyster steak.
Light the grill and prepare it for direct heat. See if you can get the grill grates close to the glowing embers for higher heat.
When you have a nice bed of glowing embers it's time to start grilling. Grill the steak on both sides until it has a nice color. Make sure you use a thermometer, as it is very important not to overcook this cut. It will be tough and chewy if you do. Target temp is 54-56° C (129-133° F).
Cut it against the grain, and serve with a chimichurri.