Preheat the oven to 350 degrees F (175 degrees C). Drizzle a large baking sheet with about 2 tablespoons olive oil.

Heat remaining olive oil in a small saute pan over medium heat. Cook and stir onion in the hot oil until translucent, 5 to 7 minutes. Add garlic and Italian seasoning; continue to saute until garlic is softened, 2 to 3 minutes. Remove from heat and allow to cool enough to handle.

Combine beef, pork, bread crumbs, Parmesan cheese, milk, onion mixture, salt, and pepper in a large bowl. Mix together using your hands as quickly as possible as overmixing can produce a tough meatball.

Form 1 1/2-inch meatballs and place on the prepared sheet.

Bake in the preheated oven until browned and no longer pink in the centers, about 30 minutes, turning them over after 15 minutes.