You can make this tangy dish even if you don't have a grill -- we've provided roasting instructions.
Blend lemon juice, oil, garlic, and rosemary leaves in a blender until rosemaryis finely chopped.
Divide chicken pieces between twolarge resealable plastic bags, and set intwo large bowls (to catch any drippings).Divide rosemary marinade between bags.Marinate chicken in refrigerator, turningbags occasionally, 8 to 12 hours.
Removechicken pieces from bags,reserving marinade in a bowl.
Place rosemary sprigs oncoals(if using a charcoal grill) or on lower rack (if using a gas grill); heat grill until medium-hot. Grill chicken pieces (onupper rack, if using a gas grill), skin sidesup, basting with reserved marinade andsprinkling with 2 1/4 teaspoons salt, 15 minutes (move pieces around grill so as notto char). Turn pieces over; continue togrill, sprinkling with 2 1/4 teaspoons saltand squeezing juice from 2 lemon halvesover chicken, until golden brown andcooked through, 15 to 30 minutes more.
TO ROAST:Preheat oven to 425 degrees, withracks in upper and lower thirds. Dividethe rosemary sprigs between two largerimmed baking sheets, spreading intoa single layer on each. Place 6 chickenpieces on each sheet; sprinkle with 2 1/4teaspoons salt. Roast in upper and lowerthirds of oven, basting twice with reservedmarinade, 20 minutes. Switch position ofsheets. Squeeze juice from 2 lemon halvesover chicken; sprinkle with 2 1/4 teaspoonssalt. Continue to roast until golden andcooked through, 20 to 25 minutes more.
Discard any unused marinade. Loosely tent chicken with foil, and let stand10 minutes. Cut chicken legs from thighs,and halve breasts crosswise.
Arrange chicken on a large platter;garnish with rosemary sprigs and remaining 6 lemon halves.
Plan ahead; the chickenneeds to marinate at least 8 hours.