In the present day, it is not uncommon for there to be a class full of engineering students with very few women among them. To combat this lack of gender diversity, colleges and universities have employed outreach programs and developed summer engagement opportunities that allow women to explore engineering before they graduate high school. The present research, an extension of work previously presented at the 2018 American Society of Engineering Education conference, was conducted at the University of Dayton to evaluate the effects of a single-sex camp and a co-ed residential engineering camp on female participants' interest in and self-efficacy related to engineering. Surveys were used to collect quantitative and qualitative data, and observation provided additional context. Data was collected at a total of four engineering camps during the summers of 2017 and 2018. Analysis of the survey responses indicated that these engineering camps have a significant impact on female participants' self-efficacy in engineering, indicating the importance of coordinating camp activities that engage participants' creativity while building their confidence in engineering. Furthermore, the way engineering camp activities are presented may affect participants' perceptions of their own abilities in engineering. These findings add to the existing body of research exploring engineering self-efficacy and the participation of women in engineering, in addition to the effects of K-12 engineering outreach and camp programming.