Subo, 50, will be the headline act at the celebratory pageant during equestrian event the Royal Windsor Horse Show.
The Britain's Got Talent runner-up will be joined by singers Katherine Jenkins, Il Divo and Michael Buble, as well as hundreds of horses and riders.
The May show, called The World Comes To Windsor, will be screened on ITV.
A source said: "This show will be a major highlight of the Queen's Diamond Jubilee celebrations. Susan is a huge global star and it's a great booking for such a prestigious event."