Pre-heat the oven to 180ºC, 350ºF, Gas Mark 4 (170ºC for fan assisted).
Fry the beef and onions with the oil in a pan until browned. Place in an ovenproof dish with the carrots and mushrooms.
Mix the Colman's seasoning with water and add to the dish.
Cover and cook in the oven for 1 3/4 hours, or until the beef is tender.
Ensure piping hot and serve immediately with crusty bread or baked potatoes.