In a large heavy-bottomed pot, heat the butter or oil over medium-high heat. Add the onion and saute until fragrant and translucent. Add the garlic and saute until golden brown.
Add the winter squash, zucchini, sweet potato, orzo, canned tomatoes, thyme, rosemary, and broth. Simmer until the vegetables are soft and cooked through, about 30 minutes.
Season the soup with salt, and black pepper, to taste. Serve with sliced crusty bread.