Research has revealed that second language learners often seem passive and reticent in language classrooms. In the age of globalization, however, there is an urgent need for English as a Foreign Language (EFL) teachers to enhance their reticent students' confidence to help them take part more actively in classroom oral activities. In line with this trend, the present study reports on action research on increasing the EFL students' confidence in speaking. A second aim was to find out about the beneficial consequences of doing action research for second language teachers in their specific classroom contexts. Participants involved in this study were 16 Iranian male university students who had participated in a general English classroom in a private English language institute. The students had an upper-intermediate level of English. In order to increase the students' confidence, 30 minutes of each session were devoted to interview technique during eight successive weeks. Insights into the students' confidence development were gained through quantitative analysis of their confidence questionnaire. The findings indicated that the students' confidence increased because of incorporating additional speaking activities into the classroom and encouraging them to collaborate with their peers. In addition, this study showed that action research has a great potential to help second language teachers become autonomous.