The tri-tip roast or steak (also called a triangle roast) is the 1 1/2 to 2 1/2 pounds of meat that sits at the bottom of the sirloin. Not only does it have a rich flavor, but also tends to be lower in fat than most other cuts. Of course, this means that it can dry out faster, but with a good marinade you really can't go wrong with this cut. Good seasonings and marinades for tri-tip are those inspired by Southwestern or Asian flavors.
The versatility of tri-tips is another factor that makes them great. Uncut, it's a fantastic roast that should be grilled indirectly for 30 to 40 minutes. You can also cut the tri-tip into 1-inch steaks, that grill up in about 8 minutes over a low to medium direct heat. As always, let your steak (or roast) sit for 5 to 10 minutes before you carve or serve it. This allows the juices redistribute and evens out the heat.
Because tri-tip is lean, be careful not to over cook it, particularly when preparing the full roast. Medium is as far as you should go with this cut. Use a meat thermometer to make sure you get it right where you want it. If you are used to grilling other cuts, this one can throw some grillers off by appearing underdone when it is ready to serve.
There are a lot of people who complain about having a hard time finding this cut. In the past, almost all of it was shipped to California or ground for sirloin burger patties. With the recent interest however, you can find this cut in many places including the large shopping club stores like Costco and Sam's Club. If you have to, try calling around. It's a great cut of meat and worth the search.