Many students struggle when they are asked to write. They may feel the lack of ideas, or they believe their ideas are not good enough. Prewriting techniques (e.g., brainstorming, clustering, and freewriting) help students develop their ability to think and their confidence in generating ideas. Collaborative prewriting activities expand students' ideas as they learn from the experiences and knowledge of their classmates. In the English as a foreign language (EFL) classroom, collaborative activities also provide opportunities for students to practice their English speaking skills and activate vocabulary needed to write about the topic. This article describes an activity using collaborative techniques for generating ideas in the classroom. The activity has been used in an EFL university writing course. For the example provided students are preparing to write an opinion essay on the following topic: "What is the most important room in the house?" (Other topic suggestions are given at the end of the article.) The objective is that students will be able to collaborate with other students to generate ideas for an essay topic and reflect on how their ideas were similar to and different from those of other students.