Preheat oven to 325 degrees. Remove and discard giblets and neck from turkey. Rinse turkey under cold running water; pat dry. Trim excess fat. Starting at neck cavity, loosen skin from breast and drumsticks by inserting one hand, palm side down. Gently push hand beneath the skin against the meat to loosen.
Arrange a thyme sprig beneath skin on each drumstick. Arrange 2 sprigs each of thyme, rosemary, and sage beneath skin on each breast half. Gently press skin to secure.
Combine poultry seasoning, salt and pepper. Sprinkle body cavity with half of the seasoning mixture. Place 2 onion quarters, 4 celery pieces and 1 spring each of thyme, rosemary, and sage into body cavity. Repeat procedure for neck cavity. Tie ends of legs to tail with kitchen string. Lift wing tips up and over back, and tuck under turkey.
Place turkey, breast side up, on rack in shallow roasting pan coated with cooking spray. Lightly coat turkey with cooking spray. Insert meat thermometer into meaty part of thigh, making sure it does not touch bone. Cover loosely with foil; bake at 325 degrees for 2 hours. Uncover; bake an additional 1 hour. Cut string holding the drumstick ends to the tail to ensure that thighs cook internally. Continue to bake, uncovered, 30 more minutes, or until meat thermometer registers 180 degrees.
Remove from oven and cover turkey loosely with foil. Let stand 20 minutes before transferring to serving platter. Garnish with herbs, if desired.