Heat the olive oil in a medium soup pot or large saucepan. Add the onion, zucchini, and carrot. Saute over moderate heat for 8 to 10 minutes, stirring often, until the onion is soft and translucent.
Add the stock, basil, bay leaf, tomatoes, and salt to the pot. Increase the heat and bring the mixture to a low boil. Add the tortellini and bring the soup back to a low boil. Cook it for 2 minutes, then reduce the heat and let it simmer for 5 to 6 minutes longer. Gently stir in the parsley and pepper during the last minute or so. Makes about 5 servings.