In a small bowl whisk together olive oil, garlic, sugar, lemon juice, orange juice, Italian seasoning, paprika, onion powder, red pepper flakes, and salt and pepper.
Place chicken in a rimmed 13-in. x 9-in. baking dish. Place parts skin side up and spread them out evenly in the pan. Pour olive oil mixture all over chicken, turning pieces to coat all sides. (If you marinated the chicken in this mixture, still add it all in). Arrange slices of lemon, orange and onion around and under the chicken. Sprinkle all over generously with thyme, rosemary, salt and pepper.
Bake uncovered for about 1 hour, or until chicken is cooked and juices run clear. Remove parts to a serving platter and garnish with additional chopped fresh herbs, if desired.