Grate zest of two of the lemons into a medium bowl. Squeeze the juice from 2 1/2 lemons, reserving remaining half lemon, and add to the zest, along with olive oil. Mix well, then pour into a large zip bag. Add the lamb chops and seal bag, turning to coat lamb with the marinade. Marinate for 1 hour at room temperature or up to three hours in refrigerator.
Prepare a medium-hot grill. Remove the lamb chops from the marinade and dust generously with the oregano. Grill 3 to 4 minutes per side for rare and 5 to 6 minutes for medium rare (or until desired doneness). Remove when done and place on a serving platter tented with foil or in a warm oven to rest, about 10 minutes.
3. To serve, spoon any juice from the platter over the chops and squeeze the juice of the remaining 1/2 lemon over them, sprinkle with salt and pepper, and serve immediately, garnished with lemon wedges cut from the fourth lemon.