The designed landscape which remains today was largely developed in the late 18th century with early Victorian additions. Documentary evidence is confined to General Roy's map of c.1750, the 1st edition OS map of 1854, and the 2nd edition OS map of c.1900. Other estate plans are thought to exist although their location is uncertain (A quantity of estate plans have been uncovered since our visit and can be made available for research).
Between the 12th century and the time of David II, the Riddel family owned the lands on which Oxenfoord Castle now stands. They were succeeded by Murrays and then MacGills, who built the original Tower House in the 16th century. James MacGill was created Viscount Oxfurd in 1651. He was succeeded by his son Robert in 1663 who carried out extensive building work on his return from a prolonged visit abroad. It is thought that he laid out much of the landscape which is illustrated on General Roy's map of c.1750. In the end, he lost much of the family fortune and part of the estates. In the absence of a male heir on his death in 1705, the estate passed through other members of the family until 1758 when it was inherited by Thomas Hamilton of Fala, a grandson of the 1st Viscount Oxfurd. His daughter, Elizabeth, married in 1760 against his will, a cousin, John Dalrymple, who succeeded to the title of Lord Dalrymple of Cousland in 1771. Sir John was a lawyer, politician, scientist and improving landlord on his estates at Cranstoun and Oxenfoord, which his wife inherited in 1779. He was a friend of Robert Adam who had been a fellow student of Sir John's at Edinburgh University and who he commissioned to rebuild the house. He was the author of the 'Essay on Landscape Gardening' originally written in the 1750s and published anonymously in 1774 as 'Essays on Different Natural Situations of Gardens', an influential work of the period. It was he who laid out the structure of the designed landscape, some of which remains today.
He was succeeded in 1810 by his son who, thirty years later, also inherited the title of 8th Earl of Stair. He was created Lord Oxenfoord of Cousland in 1841 and was made a Knight of the Thistle in 1847. He extended the park, laid out the terraces on the south and east side of the house and commissioned William Burn to design extensions to the Castle which almost doubled its size. In 1853, his brother, North, succeeded as 9th Earl of Stair. The 9th Earl continued to develop the pinetum established by his brother to the south of the house. His son, John, had married Louisa Dalrymple Hamilton, heiress of Bargany, Ayrshire, in 1846, and they became the 10th Lord & Lady Stair in 1864. They then concentrated on the development of the family home at Lochinch and little is known of Oxenfoord's development from then until 1931 when the school which occupies the Castle today was established by Lady Marjorie Dalrymple. The school leases the Castle and several estate buildings from the Oxenfoord Estate Trust and, although a school, the house still has its major contents.