Learners and teachers of a foreign language in online and blended learning environments are being offered more opportunities for speaking practice from technological developments. However, in order to maximise these learning opportunities, appropriate task-based materials are required which promote and direct student to student interaction in order to counter learners' possible reluctance to use new language structures in their target language (TL). This paper presents the provisional findings of a case study in which three groups of English as a foreign language (EFL) students worked synchronously (in Skype) in pairs with spot-the-difference pictures presented to them using three different formats: standard HTML format, the Tandem tool (a content management application which distributes the materials in real-time), and a variation of the Tandem tool interface which incorporates confirmation buttons aimed at providing a scaffold to the interactions. In order to contextualise the results from the three groups of learners, a group of native English speakers also carried out the tasks. Differences in the interactions were identified, particularly between the HTML format materials and the Tandem materials, mostly due to the fact that students were able to access both students' materials prior to the synchronous interaction, enabling them to prepare for the interactions in various ways, and in some cases, to script their conversations. Other differences were found in terms of the turn-taking, time spent on tasks, and the language used to complete the tasks. [For the complete volume, see ED574893.]