This study in the field of Second Language Acquisition (SLA) was conducted in a Spanish as a foreign language classroom. The study investigates dyadic face-to-face collaborative dialogue at the computer from a sociocultural perspective. Protocols for analysis were obtained by the transcription of audio recordings of twelve dyads/triads completing three tasks in two mediums of implementation, computer and non-computer-based. By comparing learners’ activity in the two mediums through microgenetic analysis (i.e., developmental analysis), we were able to study some specific ways in which the computer influenced the course of interaction. Specifically, the aim of the study was to investigate the value of the tasks as pedagogical instruments to support collaborative activity in the foreign language classroom; the value of collaborative activity as a source for possible restructuring of interlanguage (i.e., microgenesis); and the impact of the computer as a mediational tool in the processes of collaborative activity. Results confirm: (1) the three tasks support high degrees of collaborative activity – albeit qualitatively different; (2) language can – sometimes simultaneously – be deployed by learners both as a means of communication and as a cognitive tool to achieve linguistic development; (3) the presence of the computer seems to change the nature of collaborative activity.