Research into instructed pragmatics mainly comparing implicit and explicit instruction has gained salience in language teaching research in the last two decades. The present study was designed to investigate the effect of cognitive and interpersonal task-based instruction on EFL Learners' production of two speech acts of apology and request. To this end, 125 intermediate EFL learners were conveniently sampled, and randomly assigned to four experimental groups (EG) and one control group (CG). The four experimental groups received task-based instruction on the two speech acts of apology and request (three 30-minute sessions on each), though instruction varied in terms of general tasks types (cognitive or interpersonal) and their specific variants (cognitive: predicting (EG1; N=25) and inducing (EG2; N=25); interpersonal: co-operating (EG3; N=25) and role-play (EG4; N=25)). The control group (N=25) did not receive any speech act-specific treatment. The participants' speech act production was measured through a 16-item written discourse completion test (WDCT) as both the pretest and the posttest. The findings showed the significant effect of both cognitive and interpersonal tasks, but also the greater effectiveness of the latter for speech act production. The study has implications for pragmatic task design and classroom practice. More specifically, it shows the potential of task-based instruction and interaction for EFL learners' pragmatic development.