This thesis explores the effect and effectiveness of computer-assisted language learning (CALL) as manifested in one specific electronic role-play (ERP) which was designed for a group of final year undergraduate students of international business (with German). The ERP task was informed by a sociocultural perspective of second language acquisition (SLA) and task-based learning, and was embedded in a constructivist approach. The purpose of the ERP was to create meaningful opportunities for advanced foreign language practice for higher education students which combine their language study with their main degree course. The task mimicked professional situations, incorporating skills students would be likely to encounter in their future workplace and required them to create the outline of a marketing strategy for a product of their choice to be launched on the German market. The ERP task and its effectiveness was researched through a qualitative research approach using case study methodology which encompassed three main methods: tracing semantic strands in student-produced texts in order to explore content-learning potential, output theory to evidence potential for language learning, and grounded theory in order to explore how students appropriate the computer environment while completing the task. The case study concentrated on comprehensive data collected through the core case study which represented the 6th time the ERP was used in class. Data collected during previous ERPs was used for triangulation purposes. The findings show that the task was successful in aiding students to acquire content and language knowledge. The self-directed learning approach facilitated students to follow their interests and to determine the direction of their marketing strategy, thereby ‘owning’ the learning process and the outcome. The research highlights different learner behaviour in the computer room environment and various ways in which the affordances were utilised. This research contributes to the empirical knowledge of effect and effectiveness of open task CALL as manifested in the ERP. Through the particular research approach the thesis contributes to the methodological knowledge in CALL.