Theorists in adult education tend to believe that in order to increase effectiveness, instructors-tutors should respect adult learning characteristics. Trainees - students should be in the center of the educational process and instructors-tutors should use collaborative training techniques that offer adult trainees opportunities for real participation. Our study aims at identifying and analyzing the perceptions of postgraduate students of the Hellenic Open University (E.A.P.), as regarding the use and the effectiveness of teaching techniques during the Tutorial Group Meetings (O.S.S.)