Crumble the raw breakfast sausage into a large bowl. Add beaten egg, bread crumbs, milk, and grated onion. Mix well to combine.
Scoop out approximately two tablespoons at a time of the meat mixture with a spoon or ice cream scoop and roll between the palms of your hands to form into balls and set them on a rimmed baking sheet lined with parchment paper.
Place the meatballs in the oven for 20 minutes, or until they reach an internal temperature of 160 degrees.
Remove from the baked meatballs from the oven, let cool slightly, then serve with your breakfast favorites.
Wetting your hands with a little water will prevent the meatball mixture from sticking to your skin as you roll them between your palms.