Sauté meatballs in 2 Tbsp. hot oil in a large Dutch oven over medium-high heat, stirring often, about 6 minutes or until browned. Remove meatballs, using a slotted spoon. Add remaining 2 Tbsp. oil, and reduce heat to medium. Sauté onion, carrots, and celery 5 minutes or until lightly browned. Stir in garlic, salt, and red pepper; sauté 1 minute. Stir in tomatoes, beans, stock, and meatballs; bring to a simmer over medium heat. Cover and simmer, stirring occasionally, 20 to 25 minutes or until carrots are tender. Remove from heat, and stir in spinach. Spoon into bowls, and top with cheese.
Note: We tested with Armour Turkey Meatballs.