Barbecued Roast Sirloin on a Bun

Heat 1 burner of 2-burner barbecue, or 2 outside burners of 3-burner barbecue, to medium (250° to 300°F/120° to 150°C). Brush roast with oil; sprinkle with salt and pepper. Place on greased grill over unlit burner; close lid and cook, adjusting heat if necessary to maintain temperature, for about 2 hours or until meat thermometer inserted in centre registers 140°F (60°C) for rare, or for about 2-1/2 hours or until 150°F (65°C) for medium-rare.

Orange Barbecue Sauce: Meanwhile, in saucepan, heat oil over medium heat; cook onion, garlic, paprika, chili powder, salt and pepper, stirring occasionally, until softened, about 5 minutes.

Add tomatoes, tomato paste, sugar, vinegar, orange rind and juice, and mustard; mash with potato masher. Bring to boil; reduce heat and simmer, stirring occasionally, until thickened and reduced by one-third, about 40 minutes. (Make-ahead: Let cool; refrigerate in airtight container for up to 5 days.)

Transfer roast to cutting board; tent with foil and let stand for 10 minutes. Carve into thin slices. (Make-ahead: Place in roasting pan and pour sauce over top; cover and refrigerate for up to 1 day. Reheat in 350°F/180°C oven or over medium-low heat until hot, about 20 minutes.) Serve on rolls with sauce.

Additional information :

Tips:
Throughout the grilling, you can use an ovenproof meat thermometer inserted in centre of roast to gauge doneness and an oven thermometer placed beside roast to determine temperature of barbecue.

You can also roast in a 500°F (260°C) oven for 30 minutes. Reduce heat to 275°F (140°C); roast for about 1 hour or until meat thermometer inserted in centre registers 140°F (60°C) for rare, or for about 1-1/4 hours or until 150°F (65°C) for medium-rare.