Heat oven to 375°F. Spray 13x9-inch (3-quart) glass baking dish with cooking spray. Cook and drain pasta as directed on package.
Meanwhile, in large bowl, mix tomatoes, spinach, about half of the cheese, the olive oil and oregano; stir in cooked pasta. Spoon mixture into baking dish. Drizzle broth over pasta mixture. In same bowl, mix chicken and seasoning until well coated. Place chicken pieces over orzo mixture; cover with foil.
Bake 45 minutes; remove foil, top with remaining cheese. Bake 4 to 5 minutes longer or until juice of chicken is clear when center of thickest part is cut (at least 165°F). Top with grated lemon peel and green onions.