In a nonstick skillet, heat oil over medium heat. Add onion and cook until tender. Add zucchini and garlic, cook, stirring, for 5 minutes. In bowl, combine cheese, parsley, eggs, spinach, salt, pepper, and nutmeg; stir in zucchini mixture. Spoon into lightly greased 9-inch pie plate. Bake in 325ºF oven for 35 to 45 minutes or until set but still moist in the center. Serve hot or cold; makes 4 main-course servings.