Add the chili sauce, jellied cranberry sauce, brown sugar, and lemon juice to the insert of a slow cooker.
Use a wooden spoon to break up the cranberry sauce.
Stir until the sauce ingredients are partially combined.
Add the pre-cooked turkey meatballs to the slow cooker.
Stir gently until the meatballs are evenly coated with the sauce.
Cover the slow cooker with the lid.
Cook on low for 3 to 4 hours, or until the sauce is smooth and the meatballs are heated through.
Stir occasionally, if needed, to ensure the meatballs remain evenly coated.
Once fully heated, switch the slow cooker to the warm setting, if available.
Serve warm directly from the slow cooker or transfer to a serving dish.