Preheat the oven to 160c/325f.Heat the oil on a medium-high heat in a dutch oven or other heavy based pan. Place the beef in a bowl or bag and add the flour, salt and pepper. Toss together to coat, then add the beef to the pan. Brown the meat all over (should take about 6-8 minutes).Add the garlic,stir and cook for one minute, then add the Guinness and stock. Bring to the boil, stir and place a lid on the pan. Place int he oven and cook for 3 hours (check every hour and top up with a splash of water if needed).After 3 hours add in the in chopped peppers and courgette. Place the lid on and place back in the oven for 5 minutes. This should ensure the veg stays crunchy but is warmed through.Take out of the oven and, sprinkle on the parmesan, parsley and red onion slices, then serve with warm cous cous.