In 1965, she was aboard the maiden voyage of the scientific expedition on the Alpha Helix, the research vessel of the Scripps Institution of Oceanography at the University of California, which was coming to Australia to study the ecology of the Great Barrier Reef.
Between 1971 and 1977, Dr Jeffery was a principal scientist at CSIRO's marine biochemistry unit, then a senior principal research scientist CSIRO Division of Fisheries and Oceanography (1977 to 1981) and then senior principal research scientist and then acting chief of CSIRO Division of Fisheries Research (1981-84).