Preheat oven to 375 F. Line a rimmed baking sheet with foil and coat with nonstick spray.
Place the oats, breadcrumbs, kale, onion, Parmesan and garlic (if using) in the bowl of a food processor. Pulse to grind very well. You want everything to be ground up finely so keep going until there are no chunks or big pieces.
Add the rest of the ingredients and grind until thoroughly minced and uniform.
Form into 1-tablespoon-size meatballs and place on the prepared baking sheet.
Bake for about 18-20 minutes, or until brown and cooked through. Drain on paper towels if necessary.
Warm in your favorite marinara sauce and serve with polenta, whole grain pasta, or alongside whole-wheat toast.
Store any leftovers in an airtight container in the fridge for up to 5 days. Reheat to serve.
Freeze fully cooked meatballs in a zip top freezer bag for up to 6 months. Reheat in a simmering pot of marinara sauce or thaw overnight in the fridge and warm briefly in the microwave.
Use kale or parsley or a combination of both.
You can make these as larger golf-ball size meatballs if preferred. Bake for 22-25 minutes.
To make these gluten-free, simply use GF breadcrumbs.
You can omit the cheese to make them dairy-free, but you'll want to add 1/2 teaspoon of salt to make sure they aren't bland.