He represented Queens County in the Legislative Assembly of Prince Edward Island from 1806 to 1827.
In 1802, Macaulay began recruiting settlers for the Earl of Selkirk for a proposed settlement in Upper Canada near the current site of Sault Ste Marie.
On the island, he built a chapel on his property at Point Prim, where he also taught school.
He was granted a license to practice law by Governor Joseph Frederick Wallet DesBarres but Peter Magowan, the island's attorney general, protested this on the grounds that Macaulay had no formal legal training and was also a preacher.
In 1809, he joined the Loyal Electors, a group critical of the island's ruling elite, particularly Lord Selkirk.