Place mince, onion, oregano and lemon zest in a large bowl. Season. Using clean, damp hands mix to combine well. Roll a heaped tablespoon of mince mixture into a ball. Repeat to make 20 meatballs.
Heat oil in a large non-stick frypan over medium-high heat. Cook meatballs for 4-5 minutes or until browned. Add tomato passata, stock, zucchini, celery and carrots. Stir well, bring to the boil then reduce heat to a low simmer for 12-15 minutes or until meatballs are cooked through and sauce has thickened. Stir through spinach and season to taste.
Sprinkle meatballs with feta and extra oregano. Serve with cous cous or rice, salad and lemon wedges.
Meatballs will freeze well raw or as a cooked dish with the sauce.
Great meal to have in the freezer – cook some pasta, reheat meatballs, toss through and dinner is ready.
Swap feta for ricotta or parmesan; swap oregano for thyme or parsley.