Don't let the large amount of fresh spinach intimidate you. It cooks down to about 3 cups.
Preheat oven to 400°.
Secure turkey halves together at 1-inch intervals with heavy string. Rub surface of turkey with thyme, 1/4 teaspoon salt, and 1/4 teaspoon pepper. Heat oil in a large Dutch oven; add turkey, browning on all sides. Remove turkey from pan. Add shallots; sauté 3 minutes. Add apples; sauté 3 minutes. Return turkey to pan. Stir in cider and rosemary; bring to a boil. Cover and bake at 400° for 30 minutes. Uncover, turn turkey over, and bake an additional 30 minutes or until turkey is done and apples are tender. Remove from oven; let stand 10 minutes.
Heat a large nonstick skillet over medium-high heat. Add 4 cups spinach; sauté until spinach wilts. Place in a bowl. Repeat procedure with remaining spinach. Add 1/4 teaspoon salt, 1/8 teaspoon pepper, and margarine to spinach; toss well.
Cut turkey into 1/4-inch-thick slices; serve with apple mixture and spinach. Sprinkle with parsley.