Sirloin tip steak is lower in fat and less tender than other cuts of beef, therefore marinating it in something acidic (like vinegar or citrus) before cooking will begin to tenderize the meat fibers. You can cook the steaks on a grill, or use a cast iron grill pan on your stove to sear it on both sides and then broil for a few minutes on high in the oven. The trick to keeping it tender is to cook it only to medium-rare or medium doneness. Serve steak with Balsamic Roasted Vegetables and a Green Salad.
Place all the steaks, vinegar, oil, garlic, rosemary, salt, and pepper into a small baking dish. Use a dish that will tightly fit everything so the marinade covers the steaks. Cover and place into your refrigerator for 3 to 4 hours. Then set the steaks on your counter for at least 30 minutes to bring them to room temperature before cooking.