Spray a large frying pan with some low calorie cooking spray. Add the onions and cook on a moderate heat until they start to soften.
Add the beef and cook until all sides are browned. If your slow cooker has a saute function then you can use this.
Add all the remaining ingredients to the slow cooker, along with the onions and beef. Stir well.
Replace the lid and cook on medium for 6 to 7 hours or on high for 4 to 5 hours.
The meat should be tender and the potato should have started to thicken the stew slightly.
Pick out the bay leaf and serve.