Made with half beef and half shredded zucchini and cooked millet or quinoa, these flexitarian meatballs come together in just 30 minutes. Serve them with marinara sauce over roasted spaghetti squash or sauteed zucchini noodles.
Squeeze zucchini in a potato ricer or clean kitchen towel to remove excess moisture. Transfer to a bowl; add beef, millet, garlic, parsley, egg, 1 teaspoon salt, and 1/4 teaspoon pepper. Gently combine using 2 forks. Roll mixture into 1 1/2-inch balls and arrange on a rimmed baking sheet.
Preheat broiler with a rack in upper third. Drizzle meatballs with oil; toss to coat. Broil, rotating sheet once, until golden on top and cooked through, 8 to 10 minutes. Serve over squash, with marinara, cheese, and basil.