Authentic learning tasks, resembling life-like situations, have been effectively used in this research with Task-based Language Teaching (TBLT) of English as a Second/Foreign Language (ESL/EFL). The present study also focuses on the implementation of the Content and Language Integrated Learning (CLIL) approach in ESL/EFL teaching comparing two online courses, a course containing more "traditional" tasks with one consisting of less authentic tasks. For more meaningful learning, a sufficient level of authenticity to enable holistic teaching is required. Towards this goal, the study put into effect two e-courses, with 50 participants, differing distinctly in levels of authenticity. The Method section describes the three instruments, used to collect the relevant data, which will provide answers to the equally posed three research questions. Specifically, the Integrative Learning Value (ILV) instrument measured knowledge transfer, the Approaches to Teaching Inventory (ATI) students' learning performance in relation to more or less teacher/student-centered teaching strategies as well as the 5-Dimensional Framework for Authenticity (5DF) instrument for student perceived authenticity. Finally, results are presented and conclusions are discussed.