|1968 Mexico City||Individual jumping|
|Women's World Championships|
|1965 Hickstead||Individual Jumping|
|1970 Copenhagen||Individual Jumping|
Coakes was born in June 1947. Her father, Ralph, was a farmer in Hampshire. Her elder brothers, John and Douglas, were also on the British junior show jumping team. At the age of three she learned to ride on a donkey. In 1960, her father bought Stroller, an eight-year-old pony, originally imported in a job-lot from Ireland. Stroller was 16 at the end of Marion's junior career, and her father wanted to replace him with a larger horse, but Marion was not willing to let him go and continued showing on the pony.
In her second season as a senior Marion won the Queen Elizabeth II Cup—a former international ladies class event—that took place at the Royal International Horse Show. That year she won three Nations Cup events, helping to win the Presidents Cup.
In 1964 Marion won the Hickstead Derby Trial and placed second to Seamus Hayes in the Hickstead Derby, and the following year Marion rode Stroller to a gold medal in the ladies World Championship at Hickstead. She won the 1967 Hickstead Derby, placed second in 1968 and third in 1970. Marion competed at the 1968 Summer Olympics in both the team and the individual jumping events. In the individual jumping she won a silver medal. In 1970, Coakes won the Hamburg Derby with a clear round–the fiftieth recorded on the course and the first time by a female rider. That year Stroller was the leading show jumper Horse of the Year Show. Following Stroller's retirement, Marion continued to jump and won the Queen Elizabeth II Cup again in 1976 while riding on a new mount, Elizabeth Ann.
- Donnelley, Paul (23 July 2000). "How the Queen Mother touched our lives: The Jockey; David Mould". Sunday Mirror. FindArticles. Retrieved 21 June 2009.
- "Marion Janice Coakes". British Olympic Association. Retrieved 21 June 2009.
- "The Heroes of Hickstead". The Equestrian. 29 July 2008. Archived from the original on 20 November 2008. Retrieved 21 June 2009.
- "Stroller: Great horses in history". Horse & Hound. 13 February 2008. Retrieved 21 June 2009.
- "Hickstead's historic Queen Elizabeth II Cup downgraded". Horse & Hound. 15 February 2008. Retrieved 21 June 2009.
- "Ten British equestrian greats inducted into Hall of Fame". Horsetalk. 7 June 2006. Retrieved 21 June 2009.