Stir together the garlic, chiles, oregano and oil in a large baking dish. Add the steaks and turn to coat in the marinade. Cover and refrigerate for at least 4 hours and up to 8 hours.
Heat grill to high. Remove the steaks from the refrigerator 30 minutes before grilling to take the chill off. Remove from the marinade and season liberally on both sides with salt and pepper. Grill the steaks on both sides until golden brown and slightly charred and cooked to medium-rare and an instant-read thermometer registers 130 degrees F. Remove from the grill to a cutting board and let rest, loosely tented with foil, for 10 minutes. Slice into 1/2-inch thick slices and serve.