Tri-tip roast is a flavorful cut of beef with a rich marbling of fat, but it is less tender than a sirloin roast or a tenderloin. Slow-cooking or braising will make the tri-tip fall apart or turn it to mush. If you want a truly moist tri-tip roast that accentuates the rich, meaty flavor of the beef, grill it over medium heat.
Choose a tri-tip roast that is at least 2 1/2 pounds, so that it will not overcook quickly on the grill. Look for a rich marbling of fat and dark red meat. Avoid tri-tip roasts that are thin, because they will easily overcook, and tri-tips that are too dark or have yellowed fat, because this could be a sign of old meat.
Rub the tri-tip roast with olive oil to keep it moist on the grill, and add your preferred seasoning. Allow the roast to come to room temperature before you cook it. This will allow the beef to retain more of its juices on the grill. Grill the tri-tip for six to eight minutes per side over medium-high heat, about 400 degrees Fahrenheit. Monitor the meat carefully and use a meat thermometer to ensure that it does not overcook. For best results, cook your tri-tip to an internal temperature of 130 degrees for medium-rare, or 140 degrees for a medium roast.
Grilled tri-tip roasts are hearty enough to serve with substantial side dishes, such as baked or roasted potatoes. If you are concerned about portions or starches in potatoes, cut the tri-tip into servings of about 3 ounces each and pair them with a side of steamed vegetables or a crisp garden salad and light ranch dressing. Serve the smoky, flavorful beef with grilled sides, such as grilled onions or grilled corn on the cob.
Although the tri-tip is a not a tough or fibrous roast, it will toughen if you cook it past medium doneness. After grilling, allow the meat to rest for 10 minutes before you carve it. The resting time allows the hot juices to cool slightly and soak into the meat, which will make your meal flavorful and juicy. If you cut the tri-tip prematurely, the juices will run out and the roast will tend to be dry.