Combine cranberry sauce, BBQ sauce, brown sugar, and apple cider vinegar in a mixing bowl. Stir until smooth and well blended. Add garlic powder and red pepper flakes if using. This sweet-tangy sauce is what makes these Christmas cranberry meatballs addictive.

Place frozen meatballs in your crockpot in a single layer if possible. Pour the cranberry BBQ mixture over the meatballs. Stir gently to coat every meatball in that glossy sauce. No need to thaw the meatballs first—they'll cook perfectly from frozen.

Set your slow cooker to LOW and cook for 3-4 hours, stirring occasionally. The meatballs should be heated through and the sauce thickened into a beautiful glaze. If you're in a rush, cook on HIGH for 1.5-2 hours. The longer cooking time lets the flavors meld together.

Once cooked, switch to WARM setting for serving. These festive cranberry meatballs stay perfect for 2-3 hours on warm—great for parties. Stir occasionally to keep them coated. Serve with toothpicks in a festive dish. Garnish with fresh parsley for color.