Heather Blundell was born in Queanbeyan, New South Wales. As Heather McKay, she completely dominated the sport of women's sqash in the 1960s and '70s. She lost only two matches in her entire career (in 1960 and 1962), and was unbeaten in competitive squash matches from 1962 through to 1981, when she retired from active open squash.
McKay won her first British Open (considered to be the effective world championship of the sport at the time) in 1962. She then won it again every year for the next 15 consecutive years, losing only two games at the championship during that time. She usually won her finals matches comfortably. In the 1967 championship, she won the final against her compatriot Bev Johnson without dropping a point.
In 1976, an unofficial world championship known as the Women's World Squash Championship was held in Brisbane, which McKay won by defeating Marion Jackman in the final 9-2, 9-2, 9-0. The first official women's World Open was held in 1979 in England, and McKay captured the inaugural title with a 6-9, 9-3, 9-1, 9-4 win over Sue Cogswell in the final.
McKay also won the also won the Australian Amateur Championships for 14 consecutive times from 1960 to 1973.
When she retired in 1981 at the age of 40, McKay had gone nearly 20 years with only two defeats to her name. Since retiring from the top-level game, she has remained active in international Masters level events, and has won two over-45 world championship titles and two over-50 world championship titles.
Heather also proved to be a talent in other sports, including field hockey, where she was a member of the Australian Women's Hockey Team in 1967 and 1971. In racquetball, she won the American Amateur Racquetball Championship once (1979), the American Professional Racquetball Championship three times (1980-1 and 1984), and the Canadian Racquetball Championship five times (1980 and 1982-5).
| Year | Opponent in final | Score in final |
| 1979 | Sue Cogswell | 6-9, 9-3, 9-1, 9-4 |
| Year | Opponent in final | Score in final |
| 1962 | Fran Marshall | 9-6, 9-5, 9-4 |
| 1963 | Fran Marshall | 9-4, 9-2, 9-6 |
| 1964 | Fran Marshall | 9-2, 9-2, 9-1 |
| 1965 | Anna Craven-Smith | 9-0 9-1 9-2 |
| 1966 | Anna Craven-Smith | 9-0, 9-0, 10-8 |
| 1967 | Anna Craven-Smith | 9-1, 10-8, 9-6 |
| 1968 | Bev Johnson | 9-0, 9-0, 9-0 |
| 1969 | Fran Marshall | 9-2, 9-0, 9-0 |
| 1970 | Marcia Roche | 9-1, 9-1, 9-0 |
| 1971 | Jenny Irving | 9-0, 9-3, 9-1 |
| 1972 | Kathy Malan | 9-1, 9-1, 9-2 |
| 1973 | Cecily Fleming | 9-1, 9-0, 9-1 |
| 1974 | Sue Cogswell | 9-2, 9-1, 9-2 |
| 1975 | Marion Jackman | 9-3, 9-1, 9-5 |
| 1976 | Sue Newman | 9-2, 9-4, 9-2 |
| 1977 | Barbara Wall | 9-3, 9-1, 9-2 |
McKay was made a Member of the Order of the British Empire (MBE) in 1969, and a Member of the Order of Australia (AM) in 1979. She was also awarded the Australian Sports Medal in 2000.
McKay wrote a book, Heather McKay's Complete Book of Squash, which was released in 1979. Staying active in squash, she was named coach of the Australian Institute of Sport's Squash Division in 1985. In 1999 she was one of the founder members of the Women's International Squash Players Association Hall of Fame, of which she herself was one of the first to be inducted.
McKay was featured on the front cover of the 2006 Sensis White Pages for the Canberra, Queanbeyan and Yass regions.