Oswald, who was the racing manager for the Queen Mother and then jumps adviser for the Queen, died at 86 years old after battling a long illness.
Oswald's wife, Lady Angela, who was also a lady-in-waiting to the Queen Mother for many years, shared a sweet message about her late husband. "He always said he had the most wonderful job anybody could ever have had and that for all his working life he was simply doing what he would have done had he been a rich man who didn't have to work," she told The Racing Post.
"Sir Michael did a magnificent job managing the Royal Studs for so long. He was deeply committed to the studs, the Queen and the Queen Mother. He was extraordinarily enthusiastic and got such a buzz out of all the royal winners," the Queen's racing adviser John Warren also said about Oswald.
Oswald became manager of the Royal Studs in 1970 until the Queen Mother died in 2002. Then, he became the Queen's racing advisor in 2003. Throughout his career, the royal family's horses won twin Classic triumphs.
Nicky Henderson, a trainer of royal jumpers for over 20 years, said Oswald "had the most amazing twinkle and such a lovely impish air about him."
"He really was the most lovely man and came out with such wonderfully witty lines. He had a marvelous military background and always referred to his wife, Lady Angela, as the commanding officer," he said.
Henderson also touched upon his special relationship with the royal family. "He was very close to the Queen and the Queen Mother and loved his role with their horses," he said. "He would go absolutely anywhere to watch them run, even in the last few years when he was in his eighties. He lived in Norfolk, but would happily drive all the way to Exeter. The Queen once said to me that we had to stop Michael traveling all over the country. I did very respectfully point out she was the only one who could do that."