Appointed to a teaching position at Birkbeck College, University of London, Ferrier's focus turned from polysaccharides to monosaccharides. New laboratory tools and methods enabled their reactions and mechanisms to be studied like normal organic compounds, rather than a separate field, and he pioneered this approach. In the early 1960s as a NATO Post Doctoral Fellow, he worked in Professor Melvin Calvin’s group at the University of California, Berkeley. They were exciting times. While Ferrier was there, Calvin was awarded the Nobel Prize for Chemistry, and he also met Carolyn Tompkins, the pair marrying in Edinburgh in 1962.
Arriving in New Zealand in 1970 as Victoria University’s first Chair of Organic Chemistry, Ferrier continued to lead work on the monosaccharides, specialising in their use as starting materials for the synthesis of non-carbohydrate compounds of pharmaceutical interest. He had previously clarified the mechanism of the Fischer glycosidation and discovered an allylic rearrangement reaction of glycals, now known as the Ferrier rearrangement  – the first of two reactions that bear his name. Many of Ferrier's best discoveries were made by following up unexpected chemical observations, which often led him into uncharted territory. His second ‘name’ reaction, the Ferrier carbocyclization, was the result of this approach.
He served on the Toxic Substances Board in the 1980s and the leadership of the RSNZ report Lead in the Environment that confirmed the toxic effects of lead and began the phase-out of leaded petrol.
After his retirement from Victoria University in 1998, he became an emeritus professor. Ferrier then entered what he referred to as his supposed retirement, working with the carbohydrate chemists at Industrial Research Ltd. Here he continued to foster the next generation of carbohydrate chemists in New Zealand – his grandchildren, instilling his rigorous approach to chemistry with mentoring and assistance with the group's publications.