Preheat the air fryer to 380°F (193°C) for 3–5 minutes. Lightly spray the basket with olive oil to prevent sticking.
Make the panade. In a large bowl, combine the breadcrumbs and milk.
Stir and let it sit for 2–3 minutes until the breadcrumbs absorb the milk.
Add flavorings. Mix in the Parmesan, onion, garlic, parsley, salt, pepper, and oregano. Stir to form a paste-like mixture.
Combine the meats and egg. Add the ground beef, ground pork, and egg to the bowl. Use your hands to gently mix just until combined. Do not overmix—that can make the meatballs tough.
Shape the meatballs. Scoop about 1 1/2 tablespoons per meatball (a small cookie scoop works well) and roll into balls about 1 1/4 inches in diameter.
You should get 20–24 meatballs.
Arrange in the basket. Place meatballs in a single layer in the air fryer basket, leaving a little space between each one. Work in batches if needed.
Air fry. Cook for 9–11 minutes, shaking the basket or turning the meatballs halfway through. They’re done when the centers reach 165°F (74°C) and the outsides are browned.
Serve. Toss with warm marinara, spoon over pasta, or use for subs.
Garnish with extra Parmesan and parsley if you like.