Coat the bottom and sides of a large Dutch oven or casserole with 1 1/2 tablespoons olive oil; layer each zucchini, summer squash, tomato and onion in that order; top with 1 tablespoon herbs, salt and pepper and 1/2 tablespoon olive oil; then add 1/3 of the grated cheddar.
Repeat with a second and third layer.
Put cover on casserole and bake at 350F for 1 hour and 15 minutes.