1 1-pound loaf unsliced sourdough bread, cut into 1-inch cubes (about 16 cups)
3/4 10-ounce package ready-to-use fresh spinach, stems removed, leaves coarsely chopped (about 8 generous cups)
2 tablespoons (1/4 stick) butter
1/2 cup minced shallots (about 4)
3 celery stalks, finely chopped
4 garlic cloves, minced
2 8-ounce jars fresh oysters, drained, coarsely chopped
2 tablespoons chopped fresh tarragon or 2 teaspoons dried
3 eggs, beaten to blend
1 1/2 cups (about) canned low-salt chicken broth
Preheat oven to 250°F. Divide bread cubes between 2 large baking sheets. Bake until dry but not colored, about 15 minutes. Transfer bread to very large bowl. Add spinach to bread.
Melt 1 tablespoon butter in heavy large skillet over medium heat. Add minced shallots, chopped celery and garlic and sauté until tender but not brown, about 5 minutes. Stir vegetables into bread mixture. (Can be prepared 1 day ahead. Cover and refrigerate.)
Melt remaining 1 tablespoon butter in heavy medium skillet over medium heat. Add oysters and sauté 2 minutes. Mix oysters and 2 tablespoons tarragon into stuffing. Season to taste with salt and pepper. Mix in eggs.
Mix 1/3 cup chicken broth into stuffing. Fill main turkey cavity with stuffing.
Mix enough chicken broth into remaining stuffing to moisten (about 1/2 to 3/4 cup broth, depending on amount of remaining stuffing).
Spoon remaining stuffing into buttered baking dish. Cover with buttered aluminum foil.
Bake stuffing in dish alongside turkey until heated through, about 30 minutes. Uncover stuffing and bake until top is crisp, about 20 minutes.
Preheat oven to 350°F. Butter 13x9x2-inch baking dish.
Mix 1 1/2 cups chicken broth into stuffing. Transfer to prepared dish.
Cover with buttered aluminum foil and bake until stuffing is heated through, about 30 minutes.
Uncover stuffing and bake until top is crisp, about 20 minutes.
