Combine ingredients in ziploc bag and marinate chuck in refrigerator for 2 to 3 hours.
Wrap chuck loosely in aluminun foil with slices of onion above and below, creating a pouch with tightly rolled edges (to seal), with shiny side facing inward.
Place on grill over white hot coals or in oven at 325F degrees for 13 minutes per lb.
Side: Scrub baby potatoes and rub with olive oil. Sprinkle with coarse or sea salt. Wrap in foil. Cook alongside the chuck roast.
Submitted by: CM