Outreach camps are an effective route to increasing interest in STEM disciplines, especially for underrepresented groups. They are also common components in the broader impact plans for many early career researchers. However, there is very little basis for understanding which aspects of outreach camps lead to positive outcomes. This is due in large part to the difficulty in comparing existing camps both within specific STEM disciplines and across them. As a result, there is little science-based guidance for the development of effective outreach camp structure or content. Because of this, we specifically target the process of design in outreach camps due to its importance in engineering degree programs. By comparing different methodologies for incorporating design thinking through a qualitative multi-case study across four engineering disciplines, we have begun to assess whether design can be used to positively affect outcomes of STEM outreach camps and provide guidance for outreach development.