From 1958–1960 he worked in Jerusalem as part of the team that studied the Dead Sea Scrolls.
After a few years, he realized he needed to explore the influences on the religion of the Hebrews following their Babylonian exile, so he undertook two years of post-doctoral work at Harvard University (1964–66)[1] to study Zoroastrianism, an ancient faith born in Persia, and possibly the world's first monotheistic religion.
[1] Driven by his interest in comparative religion, Oxtoby travelled to more than a hundred countries and studied more than a dozen languages, including Hebrew, Arabic, Ugaritic and Sanskrit.
In terms of publications, Oxtoby was probably best known for the two-volume introductory textbook he edited, called World Religions: Western Traditions and World Religions: Eastern Traditions, published by Oxford University Press (1996; 2nd edn 2002).
[1] A year after her death from cancer, he married Julia Ching (1934–2001), who also died from the disease.