Coat 6-quart Crock Pot with cooking spray. Mix bread crumbs, eggs, half of the garlic, half of the onions, and basil in a large bowl. Add the turkey. Season with salt and freshly ground black pepper. Mix well. Cover and place in freezer for about 20 minutes to make handling easier.
Heat oil in large skillet over medium-high heat. Saute remaining garlic and onion until translucent and soft, about 10 minutes. Stir in remaining ingredients.
Shape meat into 20 2-inch meatballs. Add to Crock Pot in layers. Pour sauce mixture over top.
Cook for 5-7 hours on low. Our meatballs were cooked through and falling apart after 5 hours.