Preheat oven 200°C fan forced. Arrange Broccolini®, tomatoes and potatoes in a large greased roasting pan. Drizzle over 2 tablespoons oil, season. Turn to coat.
Place the chicken, breast-side down, on a clean board. Use kitchen scissors to cut along each side of the backbone to remove. Turn chicken over. Use the heel of your hand to press down on the breastbone to flatten. Pat skin dry with paper towel. Place the chicken skin side up over the vegetables.
Squeeze juice from 2 lemon quarters into a bowl. Add garlic, oregano and remaining oil. Spoon over the chicken and vegetables. Season well. Add the remaining lemon wedges to the pan. Roast for 50-60 minutes or until chicken is golden and cooked through (see tip). Cut or pull the chicken into pieces.