In Sydney Mason worked for the Colonial Architect Mortimer Lewis. He had a success in winning first and second prizes for a new Mechanics' Institute, submitting Gothic and Classical designs, a sign of the rising competition between these styles. He built wheat silos on Cockatoo Island, a task requiring engineering ingenuity. It seems that here he acquired his acquaintance with verandas. A new Government House was then under construction which had been designed by Edward Blore while Mason had still been on his staff in 1835. He may have worked on the drawings.