Group discussion is one of the methods used by teachers in the teaching and learning activities. It is an activity which can help students finish tasks by learn together. In making group discussion, usually the teachers divide the students into some group discussion using the method. Actually there are two common methods used by the teacher in forming group discussion. They are randomly-formed groups and student-formed groups. This research aims to find the kinds of group formation method in the group discussion activity, and also the teachers’ considerations in forming group discussion. This research used qualitative research and adopted descriptive qualitative research design. This research was conducted at English Language Education Department (ELED) of a private university in Yogyakarta, Indonesia. This study involved three ELED teachers as the participants. The researcher used interview in collecting the data. The research found group formation methods namely randomly-formed groups, teacher-formed groups, and student-formed groups as the method in forming group discussion. The findings also showed that there were some considerations of the teachers in forming group discussion. The considerations are the purpose of group formation, students’ ability, group size and duration, the level of difficulty of the task, fairness of the task distribution, classroom condition, and students’ participation in group discussion.