Preheat oven to 400°F. Line a rimmed sheet pan with foil. Lightly oil the surface.
Stir breadcrumbs and milk in a bowl. Let soak 5 minutes to form a panade.
Add beef, onion, Parmesan, parsley, garlic powder, Italian seasoning, salt, and pepper. Mix gently until just combined.
Fold in the soaked breadcrumbs. Avoid overmixing to keep meatballs tender.
Scoop and roll 1.5-inch meatballs. Arrange on the pan with a bit of space.
Brush tops with olive oil. Bake 15–18 minutes, until browned and 160°F in the center.
Broil 1–2 minutes for extra color, if desired. Rest 5 minutes before serving.
Serve with warm marinara, over pasta, or in toasted rolls.