Scrub the squash with a stiff brush and slice crosswise into thin slices.
Sauté the garlic in the oil in a one-and-one-half-quart pan for one minute. Add the sliced squash and continue to cook for one minute while turning the slices gently in the oil. Stir in the tomato, salt and orégano.
Cover and cook over low heat for twelve to fifteen minutes. Sprinkle with pepper to taste and garnish with parsley.