- Preheat oven to 375°F.
- Spray 8-inch square baking dish with cooking spray.
- Cut tops off peppers about ¼ inch below stems.
- Scoop out seeds and veins.
- Heat oil over medium heat.
- Add onion, and cook, stirring frequently, until softened, 5 minutes.
- Add zucchini and garlic, and cook, 5 minutes.
- Add 2 cups water, and bring to a boil.
- Cook, about 5 minutes.
- Stir in tomato, cheese and parsley.
- Spoon polenta mixture into peppers.
- Place peppers in baking dish.
- Bake until peppers are tender and polenta is golden, about 30 minutes.