Doncaster was bred at Sledmere by Sir Tatton Sykes (1826-1913), 5th bt, from the mare Marigold (ch f 1860), a daughter of the Derby winning Teddington (ch c 1848 Orlando). Running for Mr Hargreaves she had been a smart enough filly to win the Chesterfield Stakes in 1863, finish third for the One Thousand Guineas Stakes, won by Lord Stamford's Lady Augusta (ch f 1860 Stockwell), and finish second for the Oaks Stakes, won by Lord Falmouth's Queen Bertha (b f 1870 Kingston). In 1864 she'd won the Stewards Cup. In the stud however Marigold produced nothing else close to the likes of Doncaster.

Sir Tatton's father, also Sir Tatton Sykes (1772-1863), 4th bt, had established the family stud at Sledmere, Yorkshire, and in his younger days was a gentleman rider of some repute. His last winning mount, whom he had ridden in 1829 at the age of fifty-seven, was named All Heart and No Peel. It has been suggested that Doncaster, first called All Heart and No Peel, was named after this horse.

He was purchased as a yearling for 950 guineas by Scottish industrialist James Merry (1805-1877) on the advice of his trainer Robert Peck (1845-1899). He was said to have been rechristened Doncaster after the place. Merry had other classics success with the Two Thousand Guineas winners Lord of the Isles (b c 1852 Touchstone) and Macgregor (b c 1867 Macaroni), the Derby winner Thormanby (ch c 1857 Windhound) and the Oaks and St Leger winner Marie Stuart (ch f 1870 Scottish Chief).

Doncaster was described as a "well proportioned, nicely balanced horse, not too big, and with the finest quality of any of Stockwell's sons" although he stood "a little back at the knee". He stood around fifteen hands three inches and was thought to appear larger due to his "fine substance and "bold carriage".

A "severe kick on the stifle" was said to have prevented any thought of getting Doncaster ready for a two year old campaign. However, he was brought out as a three year old and won the Derby for Mr Merry as well as finishing second for the St Leger to his stable companion, the excellent filly Marie Stuart (ch f 1870 Scottish Chief). Mr Peck said he really hadn't gotten into his best form until he was five years old, and that year he won the Ascot Gold Cup and the Alexandra Plate.

Merry dispersed his stud in 1875 at which time Doncaster was purchased by his trainer, Robert Peck, reportedly for the sum of 10,000 guineas. Mr Peck sold him on almost at once to Hugh Lupus (1825-1899), 1st Duke of Westminster, for the sum of 14,000 guineas. The Duke had first considered Knight of the Garter (br c 1864 The Prime Minister) and Gladiateur (b c 1862 Monarque), but neither possessed the requisite excellence for which the Duke was said to be searching.

Installed at Eaton, Doncaster got the illustrious Bend Or (ch c 1877), without doubt his most important son, in his first crop. Muncaster (ch c 1877) also arrived that year and he proved to be a useful sort. Other sons included the St James's Palace Stakes winner Cambusmore (b c 1881), the Prince of Wales's Stakes winner Sir Reuben (ch c 1881), the Gimcrack Stakes winner Derwentwater (ch c 1885), and Rossington (ch c 1881) who became a stallion of some merit in America.

According to the reminiscences of Richard Chapman, the stud groom at Eaton, it had not occurred to the Duke to part with Doncaster. However, the visiting Empress of Austria saw him and said she would like to purchase him. Since Bend Or had by then established himself as a worthy successor, Doncaster was duly sold to the Austrian government in 1884 and sent to the Kisber State Stud in Hungary in 1885.

Among his many winners in Austria-Hungary were the Nemzeti dij winner Prado (ch c 1887), the Austria-Preis winner Benczur (ch c 1888), the Alaji dij winner Culloden (ch c 1890), the Magyar St Leger winner Duncan (b c 1890), and the Jubilaums Preis winner Virad (ch c 1890).

Doncaster died in January of 1892.