Prepare a charcoal or gas grill for high heat (450° to 550°; you can hold your hand 5 in. above cooking grate only 2 to 4 seconds). In a small bowl, combine harissa, garlic, and 1/4 cup oil; set some aside for serving. Cut lamb into 4 pieces, then brush 2 tbsp. of paste over each. Grill lamb, turning and brushing with a little more paste as you go, until done the way you like, about 10 minutes for medium-rare. Let rest 10 minutes, then slice.
For salad, mix together chickpeas, mint, lemon peel, juice, salt, onion, and remaining 1/4 cup oil. Serve lamb slices over or mixed into bean salad, with reserved harissa sauce on the side.
*Buy harissa, a North African chile-and-spice paste, in the international section of many supermarkets.
Note: Nutritional analysis is per serving.