Despite relatively recent, higher education has evolved into a consolidated field of study. This paper examines how this field evolved in Portugal. The goal was to understand when it first appeared, how it evolved over time, which scientific areas was it associated with, and what have been its main objects of study. Tight's classification of objects of study was used to inspire content analysis, which was used to systematise information on doctoral theses in higher education held or recognised in Portugal between 1970 and 2019. Descriptive statistics completed this analysis in accordance with the study objectives. The study findings reveal that the number of theses on higher education-related themes or subthemes has increased over time, particularly in the last decade. Two major clusters of objects of study were also identified, one more relevant, focusing on "Teaching" and "Learning" and Students and the other, less representative, focusing on "System Policies", "Quality", "Institutional Management", and "Academics". Moreover, findings suggest that research in higher education in Portugal is focused on the 'usual' scientific areas, namely social sciences, and education. Despite some limitations, the study adds significantly to the understanding of higher education as a field of study, opening-up new avenues for future research.