1) Season roast with salt and pepper; place over indirect heat on grill; stir together cranberry sauce and onion soup mix and heat, covered, in microwave until hot (about one minute).
2) Baste roast with cranberry mixture every 10 minutes until roast is done (internal temperature with a meat thermometer is 155-160 degrees F.), about 35-45 minutes; let roast rest about 5-8 minutes before slicing to serve.
3) Heat any leftover basting mixture to boiling, stir and boil for 5-10 minutes and serve alongside roast.
Serves 4-6, with leftovers.
Serving Suggestions This grilled roast has a smoky sweet tang from the cranberry basting sauce. Serve with grilled potato wedges, fresh green beans and French bread with a roasted garlic bulb.