Take giblets out of turkey, wash inside and out, and pat dry.
Place turkey in a large roasting pan. Liberally salt and pepper the inside of the cavity. Stuff the cavity with thyme, lemon, onion and garlic. Brush the outside of the turkey with butter and sprinkle with salt and pepper. Tie the legs together with string and tuck the wings under the body of the turkey.
Roast turkey for 2 ½ hours, basting from time to time with pan juices, until the juices run clear when you cut between the leg and the thigh.
Remove the turkey to a cutting board and cover with foil, let rest for 20 minutes. Slice turkey and serve hot.