Heat the oven to 325°F.  Place the beef, fat-side up, onto a rack in a shallow roasting pan.  Season the beef with half the black pepper. 
Roast for 1 1/2 hours for medium-rare or until desired doneness.  Remove the beef from the pan. Let the beef stand for 15 minutes before slicing.
Add the oil to the roasting pan and heat over medium heat. Add the onion, garlic, parsley and remaining black pepper to the pan. Cook and stir until the onion is tender-crisp, scraping up the browned bits from the bottom of the pan.
Stir the stock and flour in a large bowl until smooth. Add the stock mixture to the pan. Cook and stir until the mixture boils and thickens. Serve the gravy with the beef.