Preheat the oven to 180°C / 350°F / Gas Mark 4. Heat the olive oil in a medium ovenproof saucepan or casserole dish and cook the onion and garlic for a few minutes until soft and a little golden. Season with salt and pepper, add the peppers, carrots and butternut squash.
Cook in the oven for 15-20 minutes until golden and tender. Remove from the oven and add the rice, chopped thyme and stock, bring to the boil and season to taste.
Cover with the lid and place in the preheated oven and cook for 15-20 minutes, or until the rice is just cooked and all the liquid has been absorbed. Stir in the grated cheese and chopped parsley just before serving.