Preheat the Oven & Make the Marinade: Preheat oven to 160°C (320°F). In a small bowl, mix softened butter, olive oil, garlic, lemon zest, chopped rosemary, salt, and pepper to make the marinade.
Prep the Chicken: Pat chicken legs dry with paper towels—this helps the marinade stick and ensures crispy skin. Rub the marinade evenly over the chicken, including the underside.
Add Aromatics to the Pan: Place the chicken in a roasting pan. Arrange sliced onions, lemon wedges, and extra rosemary sprigs around the chicken. Add 1–2 cups of chicken broth or water to the pan to prevent sticking and create flavorful pan juices.
Roast the Chicken: Place the pan in the oven and roast for 1 hour. The aroma of rosemary and lemon will fill your kitchen, and the skin will begin to turn golden.
Baste for Crispy Skin: Spoon pan juices over the chicken to baste. Add more broth or water if the pan looks dry, then put the pan back in the oven.
Continue Roasting & Check Doneness: Roast for another 30–60 minutes, depending on the size of the legs. Baste the chicken every 30 minutes while it cooks. Chicken is done when the skin is deeply golden and the meat is tender, juicy, and almost falling off the bone.
Rest Before Serving: Remove the chicken from the oven and let it rest for 10–15 minutes before carving. This keeps the meat juicy and allows pan juices to redistribute.