Whisk 1 (12-ounce) bottle Heinz chili sauce, 1 (14-ounce) can jellied cranberry sauce, 1 tablespoon packed brown sugar, and 1 tablespoon Worcestershire sauce together in a 5-quart or larger slow cooker until the cranberry sauce is mostly smooth.
Stir in 2 (14 to 18-ounce) bags frozen cooked bite-size Italian meatballs.
Cover and cook until the meatballs are heated through and the sauce thickens slightly, 2 to 2 ½ hours on the HIGH setting or 3 to 4 hours on the LOW setting.
If you’d like a thicker sauce, cook uncovered on the HIGH setting for the last 30 minutes of cooking time, stirring occasionally.
Transfer the meatballs and sauce to a serving dish, or turn on the warm setting and serve straight from the slow cooker.
Garnish with finely chopped fresh parsley leaves if desired.
