Sprinkle the cubes of beef with the salt, pepper and flour, toss briefly to thoroughly coat the beef.
Heat the oil and butter in a Dutch oven over medium-high heat, and brown the beef. Set beef aside.
Add the bell peppers, onions and garlic to the Dutch oven and cook for 5 minutes until softened. Make sure to scrape up the yummy browned bits from the bottom of the pan. Add red wine vinegar and bring to a boil.
Return the beef to the Dutch oven with the remaining ingredients. Bring the stew to a boil, reduce the heat to low and simmer, covered for 60 minutes until the beef is fork tender. If needed, add more beef broth until stew is the desired consistency.