Preheat oven to 400 degrees F. Line a large rimmed baking sheet with parchment paper. Alternatively, if you have an oven safe baking rack that sits on top of a baking sheet, that will create even better meatballs because air will touch the bottoms and allow for even browning.
In a food processor, blend parmesan, garlic, basil leaves and red onion until well blended. It should resemble a thick pesto.
In large bowl, combine basil mixture with remaining ingredients except salt and use hands to mix until all ingredients are well combined. Do not over mix. Once blended, add salt and mix just until the salt is distributed.
Form meatball mixture into small balls, about a tablespoon in size. I like to use a cookie dough scoop to make them all the same size.
Space evenly on baking sheet about a half an inch apart. I was able to fit 40 on one baking sheet. You will most likely need to cook them in two batches.
Cook in preheated oven on prepared baking sheet until nicely browned, about 30-35 minutes. If you are unsure if they are cooked through, the inside of the meatball needs to reach an internal temperature of 160 degrees F.