The 92-year-old Queen, whose real birthday is April 21, seemed vigorous as she keenly observed the event.
After arriving at the palace, the royals assembled on the Buckingham Palace balcony to watch a fly-by by the Royal Air Force. His absence had nothing to do with his recent hip surgery.
Meghan wore a simple peach dress by Carolina Herrera, but its off-the-shoulder style was a bit too cocktail-y for such an important military event in which shoulders are usually covered.
Then it was back to Buckingham Palace for her inaugural balcony appearance. As part of the day's pomp, almost 1,000 soldiers march to Horse Guards Parade and the Royal Air Force performs a flyover (which the royals famously watch each year from the balcony at Buckingham Palace).More news: UK Supreme Court dismisses appeal to overturn N. Ireland's strict abortion laws
She made an unexpected outing at Windsor Castle less than four weeks after Prince Louis' birth.
This is the first time the royal family were joined by the new Duchess of Sussex.
The couple postponed their honeymoon by several days to attend a garden party at Buckingham Palace in honor of Prince Charles three days after their spectacular wedding last month.
Meghan, Harry and the other members of the royal family took their place in Wellington's former office which overlooks the parade ground.
Meghan Markle is still breaking protocol despite her newly minted royal status. Such was the case during Meghan and Harry's return to Buckingham Palace, when she could be seen trying to keep her hair in some semblance of order. Meghan and Harry have stated their desire to jump right in and get to work in their new roles.