In Sociocultural Theory, mediations in second language learning include (1) mediation by others (2) mediation by self (3) and mediation by artifacts, which incorporates brilliant insights for EFL contexts (Lantolf, 2000). Putting these ideas in a task-based method, the present study aimed at examining the contribution of scaffolding and private speech in improving EFL learners' skills and seeking how learners performance might link to social or interpersonal activities they engage in. Screened through an Oxford Placement Test, 54 EFL freshmen taking a reading comprehension course participated in this study and formed two randomly divided groups and pretested using a 30-item TOEFL test of reading comprehension. The control group benefited from a teacher, who paraphrased, summarized and provided the meaning of the new words and expressions. The experimental group was asked to do the same tasks through collaboration, private speech and artifacts. Students' performances were video-taped to be used for discourse analyses and provide measures of fluency, accuracy and complexity (Iwashita, Elder, & McNamara, 2001). Two types of measurements were used: 1) a final test of reading comprehension, 2) an oral presentation of a text whose readability matched that of the texts used during the experiment. The students' performances on presenting the text orally were rated based on the idea units recalled (Johnson, 1970). The data analysis revealed no difference between the two groups in the final test, but in oral presentation, the experimental group outperformed the control group.