Saute carrots, zucchini, pumpkin, onion and capsicum 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.
Cut polenta into 5cm squares and season with garlic salt and pepper. Heat enough oil in a medium frypan 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.