Lightly spray the inside of your slow cooker with cooking spray or brush with a little oil to make cleanup easier and help the cranberry glaze release from the sides.
Pour the frozen fully cooked meatballs into the slow cooker in an even layer. It’s fine if they pile up a bit; just avoid packing them in too tightly.
2 pounds frozen fully cooked meatballs
In a medium bowl, whisk together the cranberry sauce, chili sauce, brown sugar, Worcestershire sauce, Dijon mustard, garlic powder, onion powder, black pepper, and red pepper flakes (if using) until well combined. If the cranberry sauce is very firm, microwave it for 20–30 seconds first so it blends more smoothly.
1 can (14–16 ounces) whole berry cranberry sauce, 1 bottle (12 ounces) chili sauce, 1/2 cup brown sugar, 2 tablespoons Worcestershire sauce, 1 tablespoon Dijon mustard, 1 teaspoon garlic powder, 1/2 teaspoon onion powder, 1/4 teaspoon black pepper, red pepper flakes
Pour the cranberry glaze over the meatballs. Use a large spoon to gently toss and coat as many meatballs as you can. Don’t worry if every meatball isn’t perfectly coated yet—they’ll get there as they cook.
2 pounds frozen fully cooked meatballs, 1 can (14–16 ounces) whole berry cranberry sauce, 1 bottle (12 ounces) chili sauce, 1/2 cup brown sugar, 2 tablespoons Worcestershire sauce, 1 tablespoon Dijon mustard, 1 teaspoon garlic powder, 1/2 teaspoon onion powder, 1/4 teaspoon black pepper, red pepper flakes
Cover and cook on LOW for 3–4 hours or on HIGH for 1.5–2 hours, until the meatballs are heated through and the sauce is bubbly. Stir once or twice during cooking so the sauce thickens evenly and coats all the meatballs.
When the meatballs are hot, the sauce should be glossy and slightly thick. If it seems too thin, remove the lid and cook on HIGH for another 15–20 minutes, stirring a couple of times to help it reduce.
Taste a spoonful of the sauce and adjust if needed. For more tang, stir in 1–2 teaspoons of apple cider vinegar or a bit more Dijon mustard. For more sweetness, add another tablespoon of brown sugar. Let it cook 5–10 more minutes to blend.
1/2 cup brown sugar, 1 tablespoon Dijon mustard
Turn the slow cooker to WARM for serving. Sprinkle the top with chopped fresh parsley and a few whole or dried cranberries if you like. Keep the lid partially on to retain heat but prevent too much condensation from watering down the sauce.
2–3 tablespoons fresh parsley, whole or dried cranberries
Serve the cranberry meatballs straight from the slow cooker with toothpicks as a party appetizer, or spoon over rice, mashed potatoes, or buttered egg noodles for a cozy main dish.