She initially began riding for Glenmarnock Wheelers cycling club and quickly established herself as a leading amateur road racing rider. As Robert Millar, she was a relatively small man meaning she had comparatively less weight to carry uphill and she excelled as a specialist hill and mountain cyclist. She won the Scottish junior title in 1976 and was Scottish hill-climb champion the following year. In 1978, York established herself on the British scene. She was twenty-first in the Milk Race, and won the British amateur road race championship. She moved to France in 1979 to join the Athletic Club de Boulogne Billancourt (A.C.B.B.), one of Europe's top amateur teams, and quickly began winning races such the Grand Prix de la Ville de Lillers.