How to Barbecue Roast Beef

Barbecuing Roast Beef for a Crowd

​When feeding a large group at a family reunion or other special event, consider cooking a large, succulent roast of beef on a natural gas barbecue. It’s always a popular menu choice at a party.

The following information provides general guidelines for purchasing, preparing and cooking a large roast of beef on a natural gas barbecue. Cooking times are approximate, as varying weather conditions (temperature, wind and humidity) and barbecue models may influence the time required for cooking. ATCO Blue Flame Kitchen does not recommend barbecuing a large roast of beef during the winter months.


Purchasing a Roast

For 100 people, most large quantity food guidelines suggest purchasing about 30 – 35 lb (13.5 - 16 kg) boneless roast beef. This amount will provide about 1/4 lb (125 g) cooked meat per person. This is considered a standard-size serving for individuals of a mixed age group with average appetites. Increase the amount of beef to allow for heartier appetites or second helpings.

For testing purposes, the ATCO Blue Flame Kitchen purchased a boneless roast of beef (26 lb/12 kg) consisting of 2 hips of beef tied securely together by a butcher. The roast measured 14 inches in length and 8 1/2 inches in diameter at its thickest point. This amount of beef served 80 people and yielded rare, medium and well done roast beef.


Equipment and Accessories


Large Roasting Pan and Rack

The roast should be placed on a rack set inside a large roasting pan. If using a foil roasting pan, place it on a rimmed baking sheet for increased stability. To allow for proper heat circulation, choose a roasting pan/rimmed baking sheet that does not completely cover the natural gas barbecue grid. There should be at least 2 inches of space on all sides between the roasting pan/rimmed baking sheet and edges of the grid.


Meat Thermometer

Since the time required to cook a large roast may vary due to weather conditions and barbecue model variations, an accurate meat thermometer is essential for determining the degree of doneness.


Wood Chips

If desired, wood chips, such as mesquite or hickory, may be used to add a smoky flavour to the roast. Wood chips should be soaked in water before using. This produces a flavourful moist smoke and prevents the wood chips from burning up too quickly.



Prior to cooking the roast, check first to make sure that the roast, when placed on the rack in the roasting pan, will fit on the natural gas barbecue grid when the lid is down. There should be at least 1 inch of space between the top of the roast and barbecue lid.

If using wood chips, soak chips in water for at least 30 minutes; drain thoroughly. When cooking, use 1 cup soaked chips at a time. Replace as necessary.

The ATCO Blue Flame Kitchen used a total of 3 cups mesquite wood chips.

Allow roast to stand at room temperature for 30 minutes prior to cooking. If desired, season roast with a rub mixture prior to standing.

Preheat natural gas barbecue on high for 10 – 15 minutes. Turn control down to medium or to a setting that maintains a temperature of 350 - 375°F.

When using a dual burner natural gas barbecue, it may be necessary to reduce heat to low or turn one side of burner off. If this procedure is required, rotate pan occasionally to ensure even cooking. On a triple burner natural gas barbecue, turn centre burner off. If barbecue does not have an accurate heat indicator, place an oven thermometer on the grid to monitor the temperature.

Set prepared roast on rack in roasting pan. If using a foil roasting pan, place roasting pan on a rimmed baking sheet for increased stability.

Insert an oven-safe meat thermometer into thickest portion of roast, placing tip of thermometer as near to the centre of the roast as possible. Do not let thermometer touch bone or gristle.

To prevent roast drippings from burning, pour water into roasting pan to a depth of 1/2 inch (1.25 cm). Replenish water as necessary during cooking. Do not allow water to boil dry.

If using wood chips, place 1 cup soaked wood chips in a small foil pan. Set foil pan directly on barbecue grid or lava rock/ceramic briquettes. Replace wood chips with additional soaked chips as necessary during cooking.

Place pan with roast on barbecue grid. Cook roast, with the lid down, until meat thermometer registers 140°F. Transfer roast to a platter and cover with foil. Allow roast to stand for 30 minutes before carving. As this is a large roast, the internal temperature of the roast will continue to rise several degrees during standing.

The 26 lb (12 kg) roast tested by the ATCO Blue Flame Kitchen took approximately 5 – 5 1/2 hours to cook.

  • Medium

    Cook Time: 3 1/2 - 4 hours

    Serves 12

  • Medium

    Cook Time: 35 mins + 30 mins

    Serves 6

  • Medium

    Cook Time: 35 mins + 15 mins

    Serves 6