The Opies’ working papers cover a range of subjects, such as nursery rhymes, children’s literature, songs and games, childlore, language and traditions, and their historical, literary, sociological and geographical context. The files pertain to research carried out by the Opies for their various publications, as well as other related subjects that were of interest to them.

Most of the working papers consist of 'subject files', housed in hardcover binders. In these working files, which formed the basis of the Opies' published work, Iona Opie compiled, by topic, research notes and drafts, extracts of material written by children in response to the Opies’ school surveys, newspaper cuttings, journal articles and other printed material, letters from the Opies’ many correspondents, bibliographical notes, photographs, postcards and other ephemera, including extracts from 19th and early 20th century publications on rhymes and games, and newspaper cuttings and correspondence obtained from other researchers and collectors. The files also include material on rhymes, games and traditions from countries other than the UK.

Further working papers include material on children's books, research notes, bibliographical references, newspaper cuttings, and photocopies of research material.