Combine 3/4 cup orange juice and 1/4 cup syrup in a small saucepan; bring just to a boil. Remove from heat; set aside.
Preheat oven to 375°.
Remove giblets (including liver) and neck from turkey, and set aside. Rinse turkey thoroughly with cold water, and pat dry. Tie ends of legs to tail with cord, or tuck flap of skin around tail. Lift wing tips up and over back, and tuck under bird. Sprinkle poultry seasoning, 1 tablespoon grated orange rind, 1/4 teaspoon salt, and 1/4 teaspoon pepper into the body cavity and onto the bird. Stuff cavity of turkey with orange quarters and onion quarters. Place turkey on a rack coated with cooking spray, and place rack on a broiler pan. Insert meat thermometer into meaty part of thigh, making sure not to touch bone. Bake the turkey at 375° for 45 minutes. Baste turkey with the orange juice mixture; cover turkey loosely with foil. Bake turkey an additional 2 hours and 15 minutes or until the thermometer registers 180°, basting turkey every 30 minutes. Let turkey stand for 10 minutes; set the pan and drippings aside.
While turkey is baking, melt margarine in a medium saucepan over medium-high heat. Add reserved giblets andneck;sauté 2 minutes or until browned on all sides. Add water and broth; bring to a boil. Cover, reduce heat, and simmer 45 minutes. Add liver; simmer an additional 10 minutes. Remove giblets, neck, and liver from broth mixture; chop liver, and return to pan. Discard giblets and neck.
Add broth mixture to bottom of broiler pan, scraping pan to loosen browned bits. Strain mixture through a sieve over a bowl; discard solids. Remove fat from surface with a spoon. Pour the broth mixture into a saucepan; add 2 tablespoons orange juice and remaining ingredients, stirring with a whisk until well-blended. Bring to a boil; cook 1 minute or until thick. Discard skin from turkey. Serve gravy with turkey; garnish with fresh herbs and grapes, if desired.