Based on a modern motivation theory of learning, self-determination theory (SDT), this study aimed to investigate the relationships between English as a foreign language (EFL) learners' motivation to speak, autonomous regulation, autonomy support from teachers, and classroom engagement, with both quantitative and qualitative approaches. The participants of the study were EFL learners from a state university in Turkey. One hundred forty-two undergraduates responded to a questionnaire about the constructs and seven of them participated in following oral interviews. The quantitative findings showed that students' intrinsic motivation rate is higher than their other orientations and that their orientations correlated with regulation, teacher autonomy support, and classroom engagement in line with the theory. Qualitative findings also yielded that, although students are mostly intrinsically orientated, other motivational factors also play roles in their volition to speak, with the teacher seeming to be the key factor in the class as a motivation supporter. The results are helpful for language teachers and educators aiming to create an anxiety-free classroom environment for supporting learners' motivation to speak English volitionally and break language learning barriers.