After-school GEMS clubs in elementary and middle schools all over the world serve over 10000 girls. Elementary and middle school teachers are usually the leaders, though parents and interested adults can also run clubs. We have developed a model for infusing CS into the existing STEM clubs by training leaders and exposing girls to basic computer science. This model includes choosing simple CS lessons and modelling the teaching of these lessons to the GEMS leaders. This has been extremely successful in engaging and retaining the interest of the members. We also are winners of an AspireIT NCWIT grant, operating a very successful online computer programming camp. GEMS is committed to encouraging girls to see themselves as future computer scientists.