In 1887 Vasconcelos became a professor in the Faculty of Theology. In this capacity he taught various courses, including Dogmatic Theology and General Isagogics and Archaeology, Hermeneutics and Heuristics.Vasconcelos was the organizer of the University Archive from 1897 on. He played an important role in setting up the Faculty of Letters at the University of Coimbra and became its first Dean in 1911, after the Faculty of Theology was closed for lack of students. For several years he was director of the University Chapel, about which he wrote a book, using his position to protect many of the chapel's religious objects during the disturbances in Portugal after the 5 October 1910 revolution. He wrote for various magazines and newspapers, particularly for the "Correio de Coimbra", the diocese’s paper, and "O Instituto", of which he was a member of the editorial board. As a researcher he was known for his meticulousness and obsessive eye for detail, strengths that he passed on to his students. His research was mainly confined to Coimbra and its university, effectively developing the concept of local history in Portugal, but he also wrote biographies, being best known for those on the Portuguese soldier and poet, Brás Garcia de Mascarenhas and the Spanish philosopher Francisco Suárez. He was also well known for his 2-volume work on the Evolution of the Cult of Elizabeth of Aragon.