In a large saucepan cook onion and garlic in hot oil until tender but not brown. Stir in undrained tomatoes, pasta, water, mushrooms, Italian seasoning, and, if desired, ground red pepper. Bring to boiling; reduce heat. Cover and simmer about 20 minutes or until pasta is tender but slightly firm, stirring occasionally.
Stir in chicken or turkey; heat through. If desired, garnish with fresh basil leaves. Makes 4 main-dish servings.