It's so lean, the grill probably won't do it justice and you'll need to saw it into tiny pieces to save your teeth.
I always cook mine in my crockpot - make a few slits in the top, insert some cloves of garlic here and there, rub all over with salt and pepper, dump in a cup of beef broth and 1/2 cup or so of red cooking wine, cook on low for several hours (I've tried 7-10 and it comes out the same).
Maybe you can apply the principle of Swiss steak...slice it 1/2-3/4" thick and meat hammer it to the point that it's almost falling apart. Then grill the steaks on both sides. I'd recommend simmering them another 30 minutes to further tenderize, in whatever you choose - red wine, salsa, milk - with lots of s&p, to make a gravy.
Another thought would be giving it a speed cooking in a pressure cooker. Cut it into chunks instead of doing it whole.
I cooked a similar cut yesterday beef bourguignon-style in a big pot. I cubed the roast, and browned the meat in ghee. Added shallots, garlic, carrot, and celery til a little caramelized. Poured in 2 cups of cabernet sauvignon and 2 cups homemade GF beef stock. Sprig of fresh thyme, bay leaf, salt and pepper. In the oven at 350 for about 1.5 hours. Then threw in 2 cubed yams and back in for another hour(ish).
If you want to grill it, it needs to be cubed and marinated for a good long time. Makes excellent kabobs.
I love the suggestion from henny! thank you, i'm doing this right now! literally! I've seen this version before but someone suggested to cook for 18 min (or 5 min per pound) at 500...ummm that's a little worrisome! I will try this way and adjust heat as needed.
Best Recipe I have had for lean, grassfed meats:
45 minutes to 1 hour at 350 depending on size of roast (Err on the side of less done than more done because you can always throw it in a skillet for people who like it a little less pink). Rest 15 minutes and serve. This roast needs to be cooked to just between rare and medium rare to be tender unless your cooking in the slowcooker/dutch oven for 8-10 hours.