Tear bread into small pieces and place in a large bowl.
Add milk and toss to absorb milk, let soak for 5 minutes.
Drain any excess milk.
Whisk egg and add to bread.
Add onion, garlic, oregano, basil and parmesan and mix well.
Crumble ground beef into mixture.
Mix with your hands to endure everything is well blended and form into 2" meatballs.
Heat olive oil in a skillet and brown meatballs on all sides 5 at a time.
Transfer browned meatballs to slow cooker.
Add sauce and cook on High for 4 hours or low for 8 hours.