The time it takes for tri tip to cook on the BBQ is around 35 to 45 minutes depending on the size of the Tri Tip.
Flip the Tri Tip over every 5 or 10 minutes to allow both sides of the Tri Tip to evenly and fully cook.
Continue flipping the Tri Tip over until the 35 to 45 minutes is up and after 45 minutes the Tri Tip should be fully cooked.
If you have a meat thermometer the Tri Tip will be done when the internal temperature is around 110 to 115 F but you can cook it longer if you like depending on how well done you like your meat.