Oja was on the faculty of the
University of Tartu since 1975, with a year (1977-78) teaching in
Mali, and another (1980-81) doing postdoctoral research at
Aix-Marseille University in France. She served several terms as head of the Institute of Pure Mathematics at the university, and from 2009-15 she headed the Estonian School of Mathematics and Statistics. She was editor-in-chief of the mathematics journal
Acta et Commentationes Universitatis Tartuensis de Mathematica since 1998. ==Recognition==