Most postgraduates in Nigeria Universities are family and working-class students. They rarely have time to stay and study in the classroom due to pressures at home and work-place. To enhance their outcomes in the program despite their tight schedule, the use of online collaborative learning strategy was employed. Pretest-posttest, control quasi-experimental research design was used on 38 postgraduates in Science Education. The sample was selected from two Universities in south west Nigeria. Two instruments: Questionnaire on Postgraduates' Studying Challenges (QPSC) and Science Education Performance Test (SEPT) were administered on the sample. Data generated were analyzed using descriptive and inferential statistics. The result revealed that the use of Online Collaborative Learning Strategy enhances undergraduates' learning outcomes and retention in Science Education.