Schonfield was a liberal Hebrew Christian. In 1937 Schonfield was expelled from the Executive Committee of International Hebrew Christian Alliance (IHCA), of which he had been a member since 1925, (this organisation is now the International Messianic Jewish Alliance or IMJA). He later associated with Messianic Judaism for a while, but was bitterly disillusioned by the experience.
Schonfield was one of the original Dead Sea Scrolls team members.
Schonfield wrote over 40 books including commercially successful books in the fields of history and biography as well as religion. In 1958 his non-ecclesiastical historical translation of the New Testament was published in the UK and the US, titled The Authentic New Testament. This aimed to show without idealised interpretation the meaning intended by the writers while maintaining the original structures. A revised version appeared in 1985 titled The Original New Testament. In 1965 he published the controversial The Passover Plot, a book the thesis of which is that the Crucifixion was part of a larger, conscious attempt by Jesus to fulfill the Messianic expectations rampant in his time, and that the plan went unexpectedly wrong.
Schonfield followed The Passover Plot with a sequel in 1968, Those Incredible Christians. This was also described as controversial, but had less impact than the earlier book.
An additional aspect of his work was the revision of the Hebrew writing system. In The New Hebrew Typography, published in 1932, he argued for a significantly revised version of the Hebrew alphabet modelled after the Latin alphabet, including a capital-lowercase distinction, no final forms, a vertical emphasis, and serifs. This alphabet has not been adopted.
Apart from all this he founded the Mondcivitan Republic (Commonwealth of World Citizens) aiming at a Servant-Nation as a means of bringing peace and prosperity in the world. Many of his works published here pertain to the philosophy of this great thinker. The Mondcivitan archives are now housed in the Bishopsgate Institute in London which uses the material for cultural and educational purposes.