Mix all ingredients except oil just until they are well combined. Do not overmix.
Form into 8 medium balls, a little larger than a golf ball. It's easiest to just divide the meat into 8 parts as evenly as possible and then form balls from each portion.
Heat oil in large skillet. Add meatballs, gently, and brown on all sides. Remove from heat. You do NOT need to cook the meatballs all the way through. They will finish cooking in the slow cooker.