A considerable interest in using three-dimensional multi-user virtual worlds for different educational disciplines has been widely observed. Despite the potential benefits of this technology, many questions still remain open, as far as the design of appropriate activities in well-defined instructional design frameworks and their effectiveness on learning gain, according to preservice foreign language teachers' interactions. In this study, the results of three activities are presented, including foreign language teachers' continuing professional development by blending Sloodle and Open Sim in order to develop and to learn practically basic concepts that are related to information technology literacy. Three learning activities of different classes were designed and carried out by 135 (n = 135) preservice foreign language teachers' continuing professional development, using CoI presence indicators (cognitive presence, teaching presence, and social presence) as constructs of a theoretical framework, first to develop a constructivist instructional design approach and second to develop low-cost virtual learning environments. During all activities, one group of pretest or posttest design was used, and results indicated noteworthy improvement to learning outcomes, particularly to preservice teachers with low initial performance. The average preservice foreign language teacher's questionnaire score was increased from 42.3/100 to 66.1/100. The study findings proved no significant variation between the preservice teachers' learning outcomes based on their different roles and their secondary education curriculum (i.e., school stream). Lastly, a persistent pattern of high learning gain was identified, regardless of the activity's class and learning goals which were held in Sloodle and Open Sim.