Gas grills cook tri tip well. The cut is forgiving, the cook time is short, and the technique transfers cleanly from charcoal: two-zone setup, sear, finish, pull at temp. What you give up on a gas grill is smoke flavor, and that's worth honestly addressing rather than pretending the propane will somehow taste like red oak. The good news: a foil packet of wood chips gets you 80% of the way there.
Two-Zone on a Gas Grill
On a 3-burner grill, light the two outer burners on high and leave the center one off. On a 4-burner, light the two on one side and leave the other two off. The lit side is your sear zone; the unlit side is your indirect zone. Preheat with the lid closed for 10 minutes to get the grates hot and the dome thermometer past 450°F.
Adding Smoke
Wrap a handful of wood chips (oak or cherry) in a foil packet, poke 6 to 8 holes in the top with a fork, and lay it directly on the lit burner before the cook starts. Within 5 minutes it'll start smoking. A smoker box does the same job; both work. You're not trying to mimic a smoker, just adding a hint of woodsmoke to balance the propane flavor.
The Cook
Season the tri tip with salt, pepper, and garlic powder. Let it sit at room temperature for 30 minutes. Place the roast fat cap up over the hot zone. Sear 5–7 minutes per side with the lid closed (gas grills don't have the open-air ambient heat charcoal does, so you want the lid down to hold temp). Then move to the unlit side, close the lid, and hold 350–400°F until the internal hits 128–130°F. Total cook is usually 40–60 minutes for a 2-pound roast.
Worth Knowing About Gas Temps
Gas grill thermometers in the dome are notoriously imprecise. They're often 25 to 50°F off, especially on cheaper grills. Trust an instant-read probe in the meat over the dome reading. Pull at 130°F internal and let carryover do its 3 to 5°F work during the rest.