Combine onion and garlic in a skillet over medium heat. Cook until softened, 3 to 5 minutes. Transfer to a large bowl.
Add ground turkey, ground turkey breast, eggs, bread crumbs, milk, black pepper, oregano, basil, and salt to the bowl with the onions. Mix well and form into approximately 60 equal-sized balls.
Heat olive oil in a large skillet over medium heat. Fry meatballs until browned outside and no longer pink inside, about 10 minutes. Add cooked meatballs to sauce.
