As a yearling in the autumn of 1921 the filly was offered for sale at Doncaster and bought for 310 guineas by Richard "Dick" Dawson on behalf of the Vicomte de Fontarce.
[6] On 8 of June Brownhylda started at odds of 10/1 in a twelve-runner field for the 145th running of the Oaks Stakes over one and a half miles at Epsom Racecourse.
Ridden by Vic Smyth, Brownhylda tracked the leader before going to the front a furlong out and won in a closely contested finish, beating Shrove by a neck with the Aga Khan's Teresina a head away in third.
[9] In August Brownhylda contested the Yorkshire Oaks at York Racecourse and finished second to Lord Astor's filly Splendid Jay.
At the end of the year Brownhylda was put up for auction at Newmarket but failed to meet her reserve price when the bidding stopped at 5,500 guineas.
[15] At the end of the year, Brownhylda returned to the sales-ring at Newmarket and was bought for 5,100 guineas by representatives of the Aga Khan.