Abstarct: The development of speaking skills, particularly oral accuracy and fluency, remains a challenge for English as a Foreign Language (EFL) learners, particularly in countries like Iran where English is limited to classroom setting. Traditional methods of instruction often emphasize grammar and reading skills, leaving speaking proficiency underdeveloped. This study investigates the impact of structured cooperative tasks on the speaking accuracy and fluency of Iranian EFL learners at the upper-intermediate level. It followed a pretest-posttest control group design, including ten treatment sessions. This study involved 60 participants from two different institutes in Gorgan, Iran, aged 14 - 17, who were selected and randomly assigned into two groups (30 in the control group and 30 in the experimental group). The experimental group received structured collaborative strategies, whereas the control group received traditional instruction. To ensure consistency in language proficiency, the Oxford Placement Test (OPT) was administered. Additionally, two series of oral tests were utilized for pretest and posttest tests. Using Ur’s (1996) rubric scales, two fluency and accuracy components of speaking were measured. A pilot test was carried out to assess the reliability of pre- and post-tests. The results indicated that the experimental group showed a noticeable enhancement in their speaking accuracy compared to the control group (p < 0.05). In contrast, no significant difference was observed between the groups concerning speaking fluency (p > 0.05). These results indicate that structured collaborative tasks can effectively enhance speaking accuracy.