For Spinach sauce:
Saute garlic in margarine in large sauce pan 1 to 2 minutes. Stir in flour and cook over med heat 1 to 2 minutes more. Stir in milk; heat to boiling. Boil, stirring constantly, until thickened, 1 to 2 minutes.
Stir spinach and remaining ingredients into sauce. Cook, uncovered, over med heat until spinach is cooked, 5 to 7 minutes.
For Manicotti:.
Spray large skillet with cooking spray; heat over med heat until hot. Saute onion and garlic until tender, about 3 minutes. Add remaining vegetables; saute until tender, 5 to 8 minutets. Stir in herbs and cook 2 minutes more. Stir in chicken, cheese, salt, and pepper.
Spoon about 3 tablespoons chicken-veggie mix into each manicotti; arrange in baking pan. Spoon Spinach Sauce over manicotti.
To Freeze: Freeze in freezer safe container.
To Reheat: Bake at 350 degrees, loosely covered with aluminum foil, until manicotti are hot through and sauce is bubbly, 35 to 40 minutes from defrosted. 90 minutes from frozen.