Healthful Chicken Casserole

1 chicken, cooked, skinned and chopped
1 (10 oz) pkg frozen chopped spinach
1/2 cup finely chopped onion
1/2 tsp garlic powder
8 oz fresh mushrooms, sliced
2 tbsp margarine, melted
1 cup mozzarella cheese

Cook spinach according to package directions, eliminating salt;
drain well. Mix onion with spinach. Arrange spinach and onions
in bottom of 1 1/2 quart baking dish; sprinkle with 1/4 tsp of
the garlic powder.
Arrange mushrooms on top of spinach and drizzle with melted
margarine.
Place chopped chicken on top of the mushrooms and sprinkle with
1/4 tsp of the garlic powder. Top with mozzarella cheese. Place
in a 350º oven and bake for 30 minutes.