This paper summarizes the trends in research about student experiences in out-of-school time (OST) in countries of Europe. The analysis is based on a review of the content of research papers published between 1999 and 2019 in about 36 European countries. OST is recognized as an important aspect of students’ educational experiences that deserves increased research attention. A significant portion of students in all countries participate in OST activities either to improve their school performance or to engage in social activities. Under conditions where parents and students believe that the formal school system is weak, the OST educational experiences may be considered to be necessary to make a significant or necessary contribution to a student’s success compared with formal school itself. Because OST activities are undertaken in a free market their form and structure vary because of differences in the countries’ historical development, condition of public education, and the social, economic, cultural, and political factors that influence the educational systems. The analysis presents examples of how in some European countries conceptual models of OST have been expanded, adapted OST practices for regular school systems, and evaluated the outcomes. This review of the definitions of OST, of evaluations of its impact, and of the evidence for its effect on equality of educational opportunity throughout 36 European countries concludes that the studies provide contradictory messages. Greater consistency in conceptual development could be increased over time as researchers across countries review each other’s strategies and share methods and results.