Preheat oven 200°C fan forced. Combine oil, seasoning and garlic in a bowl, add juice from 1 lemon wedge. Arrange the chicken in a single layer in a greased roasting pan. Spoon half of the oil mixture over the chicken, turn to coat. Roast for 10 minutes.
Meanwhile, arrange potatoes on a microwave-safe plate. Cover with damp paper towel. Microwave 4 minutes. Transfer to a greased large roasting pan. Add the pears and Brussel sprouts. Spoon over the remaining spiced oil mixture, turning to coat. Place vegetables into the oven on the shelf above the chicken. Roast together 30-35 minutes, turning the vegetables once, until chicken is cooked through and vegetables golden.
Arrange the chicken over the pears and vegetables. Pour over any pan juices. Sprinkle with parsley. Serve with remaining lemon wedges and couscous if desired.