- Preheat the oven to 425˚F. Set the roast in a roasting pan. Brush the top and sides with the mustard. Sprinkle with the pepper, thyme and salt.
- Roast the beef 20 minutes, and then reduce heat to 325˚F. Continue roasting to the desired the doneness; about 60 minutes more should yield a medium-rare roast (see Note).
- Transfer roast to a plate, loosely cover with foil, and let rest 10 to 15 minutes before thinly slicing. If you would like jus, pour the 3 cups of beef stock into the roasting pan, simmer on the stovetop 5 minutes, pour into a gravy boat and serve with the sliced beef.
Note: Because roasts can vary in thickness, absolutely always use an instant-read meat thermometer to gauge doneness. A rare roast is done at 120˚F; medium-rare will be 125˚F to 130˚F. Remember that the meat will continue to cook when allowed to rest after cooking.
Recipe Options: Try another beef oven roast, such as top sirloin or rib-eye, instead of top round. Use regular Dijon mustard instead of grainy if you prefer its smoother texture. Use rosemary if you prefer its flavour over thyme. The roast could also be served cold; cooked to desired doneness, cool to room temperature, cover and refrigerate. Slice and serve within two days.