Combine the olive oil, orange juice, balsamic vinegar, garlic, rosemary and salt and pepper.
Place the chicken into a large shallow dish and pour the marinade over. Cover and refrigerate for 20 to 30 minutes.
Preheat the oven to 200°C. Place the chicken in a large oven dish lined with baking paper. Bake in the preheated oven for 30 to 40 minutes or until the chicken is golden brown and the juices run clear when pierced with a skewer. Baste occasionally with the marinade during cooking.