Preheat oven to 190C. Place chicken in a large roasting pan. Rub 1 tablespoon oil over the skin to coat. Season. Tie legs together with kitchen string. Roast for 45 mins.
Place onion, brown sugar, half the vinegar and 2 tablespoons of oil in a bowl. Toss to combine. Arrange onion mixture around the chicken with the garlic and thyme sprigs. Roast, adding the grapes to the pan in the last 30 mins of cooking, for a further 45 mins or until the chicken is cooked through.
Arrange the watercress, cucumber and walnuts on a large serving platter. Drizzle with remaining oil and vinegar. Season. Top with onion, grapes and chicken.
Recipe courtesy of taste.com.au
Serving size 6