He became associated with the Burmah Oil Company, and later joined forces with William Knox D'Arcy, of the Mount Morgan Mining Company, in developing the oil concessions d'Arcy had won from the Persian government.
Together, and with capital from the British Government, they founded the Anglo-Persian Oil Company, which made the Empire largely independent of other powers in the supply of petroleum, which had become of vital strategic importance.
[1] Greenway was created Baronet of Wenhaston in the County of Suffolk, in 1919, and in 1927 retired as chairman of Anglo-Persian Oil, and in recognition of his service to the nation was raised to the peerage[1] as Baron Greenway, of Stanbridge Earls in the County of Southampton.
Lord Greenway married Mabel, daughter of Edwin Augustine Tower, in 1883.
Thomas John Greenway, a prominent mining metallurgist in Australia, was a brother.