Put beef, oats, ketchup, onion, eggs, Italian seasoning, salt and pepper in a large bowl. Mix well.
Shape meat mixture into ten small balls. Turn on stove to medium-high heat. Put oil in a small fry pan. Add the meatballs. Cook and gently turn until browned on all sides. Turn heat to low.
Cover and cook 10 to 15 minutes. Drain off fat.
Mix ketchup, water and mustard in a small bowl. Pour over meatballs. Cover and cook 5 minutes longer.
When frying ground meat you can drain the fat off after cooking, this will make the meal healthier.
These meatballs go well with brown rice or whole-wheat pasta, and half a plate of green vegetables.