We grill on a Weber Genesis Gas Grill and this is the method for gas-grilling this beef.
1 tri tip roast (usually around 2 1/2 lbs)
1. Turn on all three burners on the grill and heat to around 500 degrees but hotter is fine.
2. Meanwhile, rub kosher salt into the meat all over--use more than you need because it will fall off a little on the grill.
3. Once the grill is hot, place the meat over the center burner area in the center of the grill. Sear the meat--this should take around 5 minutes.
4. Once the meat has a nice crust, flip it over--watch out for flareups especially if you are using the un-trimmed variety.
5. Sear the other side of the meat for an additional 5 minutes. Now turn off the center burner but don't move the meat. This is called cooking on indirect heat.
6. Check the meat every 5-7 minutes for doneness. Ours took about 20 or so minutes to get up to 140 degrees in the thickest part. Actually, it wasn't as rare as I like it but it was a perfect medium for Joey.
7. Let rest a few minutes before cutting and then slice it from the thin edge into thin slices.