Prepare onion, garlic, and celery. Heat 1 tablespoon broth in medium soup pot. Healthy Sauté onion, garlic, and celery in broth over medium heat for about 5 minutes stirring often.
Add rest of broth, tomato sauce, and Italian herbs. Simmer for another 25 minutes.
Drain and rinse both oysters and clams. If oysters are big, add to chowder about 2 minutes before canned clams. Heat for another 5 minutes. Season with salt and pepper to taste and sprinkle with chopped parsley.