In a large mixing bowl, combine ground beef, breadcrumbs, chopped onion, parsley, egg, garlic powder, salt, and pepper. Mix until well combined.
Form the mixture into small meatballs (around 1 inch in diameter). You should get about 20-25 meatballs.
In a separate bowl, mix together the cranberry sauce, soy sauce, Dijon mustard, brown sugar, and apple cider vinegar until smooth.
Place the meatballs in the slow cooker and pour the cranberry sauce mixture over them, making sure they are well coated.
Cover the slow cooker with the lid and cook on low for 4-6 hours, or on high for 2-3 hours until meatballs are thoroughly cooked and tender.
Once cooked, gently stir to coat the meatballs in the sauce before serving.
Notes
Serve the meatballs on a bed of fluffy rice or mashed potatoes, drizzled with extra cranberry sauce, and garnish with fresh parsley for a pop of color.