01 - Preheat the oven to 425°F.
02 - Pat the lamb dry. Use a sharp knife to make small incisions all over the leg, then insert halved garlic cloves into the openings.
03 - Combine olive oil, rosemary, thyme, salt, pepper, and lemon zest in a bowl. Rub this mixture thoroughly over the lamb.
04 - Place quartered onions, carrot chunks, and the halved garlic bulb into a large roasting pan. Set the lamb atop the vegetables.
05 - Roast the lamb for 20 minutes at 425°F.
06 - Lower oven temperature to 350°F. Pour white wine or chicken stock into the pan. Roast for an additional 1 hour and 10 minutes, basting once or twice. Cook until internal temperature reaches 130°F for medium-rare or desired doneness.
07 - Remove from oven and tent loosely with foil. Let rest for 15 to 20 minutes before slicing.
08 - Slice the lamb and serve alongside the roasted vegetables and pan juices.