We did this on our grill for dinner. Very tasty, although my kids complained it wasn't as well done as they preferred. But with tri-tip, if you cook it too long, the meat gets really tough. Tri-tip steaks are fairly lean and usually cut fairly thick. You want to cook them somewhere between medium-rare and medium, still very pink to red in the center. After they are cooked and rest for a few minutes, slice them nice and thin against the grain. You don't want long strings of meat, but very thin slices. It helps the tenderness of the cut.
Grilled Tri-Tip Steak
2-3 lb tri-tip steaks, cut 2-3 inches thick
2 t. lemon pepper seasoning
2 t. salt
1 t. ground black pepper
1 t. paprika
1 t. garlic powder
1 t. dried rosemary
Mix all the spices together. Rub into the steaks, making sure to cover both sides and the edges. Let them sit on a plate for a couple of hours.
Heat your grill nice and hot. If you have a thermometer, you want it at 500-600°F. Slap the steaks on the grill and cook for 2-3 minutes per side, this should give you a good char. Move the steaks to the upper rack if you have one, or off to one side away from the direct heat. Cover and cook for another 20-30 minutes over the lower heat until the meat is done to your liking, or almost done. You want it slightly under-done. Set the meat on a cutting board and cover loosely with foil. Let it rest for 5-10 minutes.
Slice against the grain into thin slices. Serve warm.