For sauce, in a large saucepan cook onion, celery, and garlic in margarine or butter until tender. Stir in fresh or undrained canned tomatoes, mushrooms, green pepper, sage, sugar, salt, and pepper. Bring to boiling; reduce heat. Simmer, uncovered, for 40 minutes. Add summer squash or zucchini. Cook about 5 minutes more or until sauce is desired consistency and squash is tender.
Meanwhile, cook tortellini according to package directions. Drain. Toss tortellini with sauce. Makes 4 main-dish servings.