To make the meatballs—in a large bowl combine ground beef, Italian breadcrumbs, egg, milk, parmesan cheese, 1 ½ tablespoon of garlic, 1 teaspoon salt, ½ teaspoon ground black pepper, and parsley. Shape the mixture into small-medium sized meatballs.
Heat a large skillet to medium-high heat. Add 3 tablespoons of olive oil and cook the boneless ribs on one side until browned, flip them over, and cook on the other side until browned.
Transfer to the slow cooker.
Add the prepared meatballs and the sausage link slices to the pan and cook until browned (you may have to cook them in batches depending on the size of your pan). Transfer to the slow cooker.
In the same skillet add the remaining tablespoon of olive oil over medium heat and add the onion.
Cook the onion for 3-4 minutes and then add the minced garlic and cook for 30 seconds. Transfer the onion and garlic to the slow cooker.
Add the crushed and diced tomatoes, salt, and pepper to the slow cooker on top of the meat mixture.
Turn the slow cooker on high and cook for 5-6 hours or until the meat is fully cooked and the boneless ribs pull apart easily. Serve with pasta.