Spinach Parmesan

2 (10 ounce) packages frozen chopped spinach
1 (8 ounce) container sour cream
1/3 cup Parmesan cheese
1/3 teaspoon garlic salt
3 slices white bread, cubed
3 tablespoons margarine, melted

Cook spinach according to package directions. Drain and press water out of spinach. Mix spinach, sour cream, cheese and garlic salt. Pour into buttered baking dish and top with bread cubes. Pour margarine over bread cubes. Bake at 350 degrees F until bread cubes are lightly browned, about 20 minutes. Can be prepared ahead and refrigerated before baking.