Preheat oven to 325°F (163°C). Remove giblets from turkey and pat the turkey dry with paper towels.
In a small bowl, mix together softened butter, olive oil, salt, pepper, rosemary, and thyme.
Rub the butter mixture all over the turkey, including under the skin. Stuff the cavity with onion, lemon halves, and garlic.
Place the turkey breast side up on a rack in a large roasting pan. Tuck the wings under the body and tie the legs together with kitchen twine.
Roast turkey in the preheated oven for 3 ½ to 4 hours, basting occasionally with pan juices, until a thermometer reads 165°F (74°C) in the thickest part of the thigh.
Remove turkey from oven, tent with foil, and let rest for 20-30 minutes before carving and serving.
Notes
Make sure to baste the turkey for a juicy outcome.