Preheat the oven to 180°C and spray a roasting tin with low-calorie cooking spray.
Scatter the potatoes over the roasting tin, spray well with low-calorie cooking spray and season with a little salt and pepper.
Place in the oven and roast for 25 minutes.
While the potatoes are cooking, place all the ingredients for the meatballs in a bowl and thoroughly mix together. You can fry a penny-sized piece of mix, to taste and season with salt and pepper according to your taste. Roll the mixture into 24 evenly-sized balls.
After 25 minutes, remove the potatoes from the oven. They should be starting to brown and soften.
Add the peppers and onions to the tin and arrange the meatballs on top; spray with low-calorie cooking spray and return to the oven for 20 minutes.
Mix the passata with the balsamic vinegar and remaining garlic granules and oregano.
After 20 minutes, pour the passata into the roasting tin with the meatballs and veggies. Stir and then tear the mozzarella into small pieces and scatter over the top.
Return to the oven for 15 minutes until the sauce is bubbling and the cheese has melted.