Parker was one of the primary architects of the Thirty-nine Articles, the defining statements of Anglican doctrine. The Parker collection of early English manuscripts, including the book of St Augustine Gospels and "Version A" of the "Anglo-Saxon Chronicle", was created as part of his efforts to demonstrate that the English Church was historically independent from Rome, creating one of the world's most important collections of ancient manuscripts. Along with the pioneering scholar Lawrence Nowell, Parker's work concerning the Old English literature laid the foundation for Anglo-Saxon studies.