Prepare the Meatballs:In a large mixing bowl, combine the ground beef or pork, breadcrumbs, grated Parmesan cheese, milk, egg, minced garlic, dried oregano, salt, and pepper. Mix until well combined.Shape the mixture into small meatballs, about 1 inch in diameter, and place them on a baking sheet lined with parchment paper.
Brown the Meatballs (Optional):If desired, you can brown the meatballs before adding them to the slow cooker. Heat a skillet over medium heat and add a bit of oil. Cook the meatballs in batches until browned on all sides, then transfer them to the slow cooker.
Make the BBQ Sauce:In a mixing bowl, whisk together the barbecue sauce, ketchup, brown sugar, Worcestershire sauce, apple cider vinegar, smoked paprika, garlic powder, salt, and pepper until well combined.
Cook in the Slow Cooker:Pour the BBQ sauce over the meatballs in the slow cooker, making sure they are evenly coated.Cover and cook on low heat for 4-6 hours or on high heat for 2-3 hours, or until the meatballs are cooked through and tender.
Serve:Once the meatballs are cooked, serve them hot directly from the slow cooker. You can garnish with chopped fresh parsley or sliced green onions, if desired.
Enjoy:Serve the Slow Cooker BBQ Meatballs as an appetizer with toothpicks for easy serving, or as a main dish with mashed potatoes, rice, or a side of vegetables.