Rub tri-tip with 1 tablespoon olive oil then, season well with garlic salt, pepper and Italian seasoning. Cook over direct, medium-high heat, fat side down for 5 minutes (it will flame up, don’t worry). Flip and cook indirectly, lid closed, side burners at medium heat for 20-25 minutes depending on your tri-tip size. Remove from grill and cover with foil for 10 minutes before slicing.