Preheat oven to 350°F.
In a large bowl, combine the bread and milk. Let sit 2–3 minutes to soften.
Add beef, egg, Parmesan, garlic powder, onion powder, parsley, salt, pepper, and olive oil. Mix gently until just combined.
Divide into 10 meatballs.
Heat a large oven-safe skillet over medium-high heat with olive oil. Add meatballs in batches, browning 2–3 minutes per side.
Pour tomato sauce over meatballs. Top each with a slice of mozzarella and a sprinkle of Parmesan.
Cover and bake for 15 minutes, then uncover and bake 5 more minutes.
Optional: Broil 1–2 minutes for golden, bubbly cheese.
Cool slightly, then serve with pasta, crusty bread, or a side salad.