Crockpot Smoked Sausage Soup

2 Cups onion, chopped
2 Tablespoons butter or margarine
2 Cups cooked chicken, cubed
1 Pound cooked smoked sausage, cut into bite-size pieces
3 Cups celery, sliced
3 Cups summer squash, sliced
2 Cups chicken broth
1 1/2 Cups fresh parsley, minced
1 (8 oz) Can tomato sauce
2 Tablespoons cornstarch
2 Tablespoons poultry seasoning
1 Teaspoon dried oregano
1 Teaspoon ground cumin
1 Teaspoon liquid smoke, optional
1/2 Teaspoon pepper

In a skillet or microwave, cook onion in butter softened. Transfer to a 3 quart or larger crockpot. Add remaining ingredients, stirring to blend. Cook on HIGH for 5 to 8 hours.