For the turkey: Preheat oven to 325 degrees F. Place the turkey on a rack in a roasting pan. Generously season the inside cavity of the turkey with salt and pepper. Stuff it with the peaches, lemon quarters, thyme, and rosemary. Tie the drumsticks together with 100% cotton kitchen string or twine. Tuck the wings under the body to keep them from burning. Brush turkey with 2 tablespoons melted butter. Generously season the outside of the turkey with salt and pepper. Roast for 2 1/2 hours.
Meanwhile, make the peach glaze: Melt 2 tablespoons butter in a small saucepan over medium heat. Add the onion and cook until tender, about 4 minutes. Add the preserves, orange juice, vinegar, mustard, and 1 teaspoon salt. Bring to boiling; reduce heat and boil gently, uncovered, for 35 minutes or until thickened, stirring occasionally.
Cut string or band of skin. Continue to roast for 30 minutes to 1 1/4 hours or until a meat thermometer registers 175 degrees F when inserted deep into the thigh (but away from the bone), brushing with 1/2 cup of the peach glaze during the last 20 minutes of roasting time. Cover turkey loosely with foil during roasting, if necessary, to prevent overbrowning. Remove the turkey, cover with foil, and let it rest for 15 minutes before carving. Serve with remaining peach glaze.