This qualitative study was designed to introduce STEM (Science, Technology, Engineering, Mathematics) activities to preservice science teachers and identify their views about STEM materials. In this context, a competition was organized with 42 preservice science teachers (13 male- 29 female) who took Instructional Technologies and Material Development course in Elementary Science Education Department in Siirt University. The competition consisted of 5 categories: balloon powered car, mousetrap car, water rocket, spaghetti bridge 1 (durability) and spaghetti bridge 2 (visuality). Structured interview form developed by researchers was used as data collection instrument. The results were analyzed with the conventional content analysis. Results indicated that participants (especially females) are more willing to use STEM materials in their future teaching life. Participants mostly believe that STEM materials facilitate learning, enhance retention and increase self-confidence. However, there are also pre-service science teachers who believe that preparation of STEM materials is difficult, takes too much time and not appropriate to students' levels.