How long to cook asparagus on a BBQ?
I sometimes steam asparagus before sautéing on a high heat with some lemon juice to get some caramelization on the outside of the asparagus. You could adapt this idea to the grill by sealing the asparagus in tin foil with a little water and steaming for four minutes (for finger thick spears). Then give them a bit of colour by placing them directly over the grill for a minute.