1. If you are using a frozen turkey, remove the turkey from the freezer several days before roasting day and let it thaw.
2. Remove the turkey from the refrigerator and rinse turkey with cool water. Pat dry with paper towels. Let it rest on a baking sheet for 2 hours until it comes to room temperature.
3. Meanwhile, place all the ingredients for the lemon-herb butter into a food processor. Pulse for 1 - 2 minutes until well incorporated. Remove from food processor, and set aside.
4. Set rack at lowest position in oven and preheat to 325°F. Sprinkle main turkey cavity with salt and pepper. Starting at neck end of turkey, carefully slide hand between skin and meat of breast to loosen skin. Spread lemon-herb butter over the breasts, under the skin. Spread remaining butter over the outside of the turkey. Sprinkle the outside of the turkey with salt and pepper. Fill main cavity with lemon and orange wedges, and parsley and thyme sprigs. Tie legs together loosely to hold shape. Tuck wing tips under.
5. Place turkey on rack set in large roasting pan. Roast turkey until thermometer inserted into thickest part of thigh registers 165°F to 170°F, about 3 hours. Cover loosely with foil while roasting, if turkey begins to brown too quickly. Tilt turkey so juices from main cavity run into pan. Transfer turkey to platter. Tent very loosely with foil; let rest at least 30 minutes (internal temperature will rise 5 to 10 degrees). Reserve pan.
6. Scrape juices and browned bits from reserved roasting pan into large glass measuring cup, skim off fat. Reserve 2 tablespoons. Add 1 cup chicken stock to juices.
7. Heat reserved 2 tablespoons fat in heavy large saucepan over medium-high heat. Add garlic and saute 2 minutes.
8. Pour drippings into a small saucepan; skim fat. Combine flour and remaining broth until smooth; whisk into the pan. Bring to a boil; cook and stir for 2 minutes or until thickened. Add flour and whisk until golden, about 4 minutes. Add degreased pan juices and 2 cups stock. Bring to boil, whisking until smooth. Reduce heat and simmer until gravy is reduced to desired consistency, about 4 minutes. Whisk in 2 tablespoons reserved lemon butter and chopped parsley. Season with salt and pepper.