Saute carrots, zucchini, squash, onion and bell pepper in a large saucepan with a small amount of olive oil. Season with garlic salt and pepper. Saute vegetables for approximately 5 minutes and pour in spaghetti sauce. Stir, cover and simmer until vegetables are slightly tender.
Slice polenta into 1/2 inch circles and season with garlic salt and pepper. Heat enough oil in a medium skillet so as to completely cover the entire bottom of the pan. Pan fry seasoned polenta in hot oil, about 3 minutes per side. Remove from oil and layer the slices in a large casserole dish. Spoon the vegetable mixture over the polenta and then sprinkle with Mozzarella and Parmesan cheese.
Bake casserole for 30 minutes. Remove from oven and let cool for 5 minutes before serving.