Place asparagus in a large ziplock bag or 13x9 glass pan and cover generously with Italian dressing. You may not use the whole bottle, just enough to coat them nicely.
Cover and place in the refrigerator for at least 30 minutes or overnight. When ready to grill remove from dressing and place on a preheated grill (we like to grill these on grill mats to make it easier). Grill until they reach your desired level of doneness. We like them with a little bit of crispy black spots, but you can grill them more or less depending on your preference.
When finished place them on a platter. If desired you can toss in remaining dressing from the marinade or just serve as is without extra dressing. We have done both depending on our mood, but most often serve it without additional dressing.