Fill a large saucepan with one to two inches of water, and add your potatoes, carrots, cauliflowerets, and green beans; Bring to a boil over high heat, reduce to simmer, cover and cook for approximately 10 minutes.
Remove from heat and drain in colander.
If you wish to save the juices for another use, make sure to drain the veggies over a dish to catch the juices.
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Heat oil in large skillet over medium high heat and add your onions and garlic.
Stir and saute them until they are soft, approximately 3-5 minutes.
Add your tomatoes, salt and pepper, and thyme, and stir, reduce heat to simmer, and cover and cook for 5 minutes to allow flavors to develop.
Remove from heat and keep covered; set aside.
Spread potato mixture over bottom of greased medium casserole or baking pan, add salt and pepper to taste, and then sread half of your tomato mixture over the potato layer.
Continue by layering your zucchini slices and chopped green pepper on top of the tomato mixture, and then pour the remaining tomato mixture on top of the zucchini-green pepper layer.
Bake in oven, covered, for approximately 50 to 60 minutes until all of your veggies are tender.