Britain's Queen Elizabeth will join 100,000 at a barbecue in Australia.

The monarch and her husband the Duke of Edinburgh will mingle with the crowd at the public event, dubbed 'The Big Aussie BBQ', in Perth's Langley Park on October 29, their final engagement on a 10-day tour of the country.

This is our opportunity to truly showcase Western Australia - our people, our food, our hospitality - to the royal couple and the world through the international media.

It is believed Premier Colin Barnett suggested the public barbecue to the queen when he visited Buckingham Palace in June, and she thought it would be a "fun" way to finish the trip - the most casual and informal event she has ever attended in the country.

Mr. Barnett said: "Numerous barbecue stalls will be located throughout the area and volunteers will be cooking sausages which can be bought via a gold coin donation.

"This is our opportunity to truly showcase Western Australia - our people, our food, our hospitality - to the royal couple and the world through the international media."

The monarch has also been invited to officiate in a sports match when she visits Clontarf Aboriginal College.

Clontarf Foundation chief executive Gerard said: "It truly is a great honour.

"We will give her a tour and the boys will play a footy match for her. The royal whistle will be there if she wishes to umpire as well."

The official itinerary for the trip showed the couple will undertake more than 20 official engagements on the tour, with stops in Canberra, Brisbane, Melbourne and Perth.