Harold Orel's research materials comprise notes, bibliographies, newspaper clippings, and scholarly articles, as well as applications for various research grants and fellowships. His research materials concern the following topics: Thomas Carlyle, Charles Darwin, Sir Arthur Conan Doyle, Gilbert and Sullivan, Lady Gregory, Thomas Hardy, Richard Holt Hutton, James Joyce, Rudyard Kipling, Augustus Pitt Rivers, Russian literature, Victorian era, and Rebecca West.