During his leisure at Oxford he collected material at the Bodleian Library and college libraries for his books. It was during these years that he met Elias Ashmole, who later became his son-in-law. Following the surrender of Oxford in 1646 Dugdale returned to Blyth Hall and compounded for his estates under the terms of the Oxford articles. Hatton, who had opposed the surrender, went into exile in France, where Dugdale visited him in 1648. He recommenced his antiquarian researches, collaborating with Roger Dodsworth on the "Monasticon Anglicanum", the first volume of which was published in 1655. In the following year he published his own "Antiquities of Warwickshire", which was soon recognised as a model county history. In this work he was one of the first to consider the significance of stone tools, stating these were "weapons used by the Britons before the art of making arms of brass or iron was known".