Engineering design practices in STEM education focus on reflecting the discipline-specific work of engineers in a manner that is suitable for the student level and course learning objectives. Using an engineering design context also facilitates student identification of global problems and feasible solutions to address such problems. In this article, within the framework of STEM approach, an engineering design activity that can be applied in middle school mathematics course is presented. Additionally, examples of students' experiences of the engineering design-based mathematics activity are given. The "Cold Storage Design Activity" was executed in a classroom setting, and the implementation process underwent examination and evaluation. 12 eighth-grade students from a middle school in Turkey took part in the implementation. The middle school were able to successfully perform an engineering design process and effectively overcome challenges through teamwork. The results of the activity show that middle school students are excited and eager to participate in a design activity.