1Heat 1 inch water to boiling in 3-quart saucepan. Add potatoes, carrots and beans. Heat to boiling; reduce heat. Cover and simmer 10 minutes; drain.
2Heat oil in 10-inch skillet over medium heat. Cook onions and garlic in oil, stirring occasionally, until onions are crisp-tender. Stir in tomatoes, cauliflowerets, celery, salt, thyme, marjoram and pepper. Cover and cook 5 minutes.
3Heat oven to 350ºF. Grease 3-quart casserole.
4Place potato mixture in casserole. Spread half the tomato mixture over top. Layer with zucchini and bell pepper. Top with remaining tomato mixture. Cover and bake 50 to 60 minutes or until vegetables are tender.