Prince Harry, Duke of Sussex and Meghan Duchess of Sussex attend the Trooping the Color ceremony in London, June 9, 2018.
The couple will follow in the footsteps of Prince Harry's parents, Charles and Diana, whose first overseas tour after their marriage also took in Australia and New Zealand.
In her first Trooping the Colour appearance, Meghan, 36, stunned in a pale pink, off-the-shoulder Carolina Herrera number and Philip Treacy hat. Princess Charlotte made her first appearance at 13 months and George shortly before his 2nd birthday.
The royal colonels, all on horseback, will accompany the Queen: Prince of Wales, Colonel of the Welsh Guards, the Princess Royal, Colonel of the Blues and Royals, and the Duke of Cambridge, Colonel of the Irish Guards.
But her late mother-in-law, strictly speaking, should not have even been at parade because, at the time, she had not yet married into the Royal Family.
Her book titled, 'Harry: Life, Loss and Love,' derived a huge chunk from the lives of Meghan Markle and Prince Harry during the early days of courting where Meghan was heavily cornered by the media for her relationship and her standing in the stereotypical British Royal protocol. Queen Elizabeth and Prince Philip stayed their in 2005.
"His attendance, alongside the Duchess of Sussex, will be a wonderful highlight for the more than 500 competitors and thousands of spectators", Mr Turnbull said.
"The joke is that Harry is Meghan's surprise stylist". "It's definitely understood that there would not have been any looks today that would have been too far past the line, as Meghan was gathered with the entirety of Harry's family, but we can't think of another time when so much skin was on display at such a formal event".
The pair have been invited to Australia and New Zealand by the countries' governments and will travel to Fiji and Tonga at the request of the UK Foreign Office.
Prince Harry, a former soldier who served in Afghanistan, founded the Invictus Games in 2014.