This article discusses a framework for the development of tasks in a synchronous online environment used for language learning and teaching. It shows how a theoretical approach based on second language acquisition (SLA) principles, sociocultural and constructivist theories, and concepts taken from research on multimodality and new literacies, can influence the design and implementation of tasks for computer-mediated communication (CMC). The findings are based on a study conducted at the Open University, a study which examined all three levels of theory, design and implementation. The paper first presents the underlying theories in more detail before examining how these theories are translated into the design of tasks for language tutorials via an audio-graphic conferencing tool. Finally it looks at how the design was implemented in practice by focusing on a number of issues such as student-student and student-tutor interaction, feedback, use of multimodal tools, and the differences between teaching face-to-face and online.