Preheat oven to 400 degrees F. Prep a 9x13 baking dish with cooking spray.
Mix ground beef, ground pork, garlic, bread crumbs, buttermilk, onion, eggs, Parmesan cheese, parsley, oregano, salt, and pepper by hand until just combined, careful not to over-mix.
Use a 1/4 - 1/3 cup scoop and form meatballs. (I use about 1/3 cup) Place the meatballs in the baking dish.
Bake for 20 minutes.
Lower oven temperature to 375 degrees F.
Place meatballs on a plate. Drain excess grease from the baking dish.
Pour about 1 cup marinara sauce in the bottom of the baking dish and spread to cover.
Place meatballs in the pan in a single layer.
Pour remaining marinara sauce over the top of the meatballs, then sprinkle the shredded Italian cheese blend over the top, so all the meatballs are covered in cheese.
Cover with foil and bake for 20 minutes.
Remove foil and bake, uncovered, for another 10-15 minutes, until the cheese is bubbly and golden.
Garnish with fresh parsley if desired.