Preheat a grill to medium high and brush the grates with vegetable oil. Put the potatoes in a microwave-safe bowl, cover and microwave until just tender, about 5 minutes. Toss the beef with the olive oil in a large bowl and season with salt and pepper. Thread the beef, potatoes and asparagus onto eight 10-inch skewers.
Combine the ketchup, mustard, vinegar, 2 tablespoons water, the Worcestershire sauce, steak sauce and red pepper flakes in a small bowl. Grill the kebabs, turning occasionally, until marked, about 6 minutes for medium rare. Serve with the sauce.