Previous research studies have shown that virtual reality (VR) learning is effective for various topics of learning (e.g., social adaptation and skills, job interview, empathy, etc.) on the autism spectrum disorder (ASD) population. VR learning is always delivered using VR devices or installations. Compared to VR installations such as Cave Automatic Virtual Environment (CAVE), with the careful design of VR software, VR headsets can achieve a similar degree of immersion and interactivity at a fraction of the cost, while keeping the whole setup highly portable and requirements on the venue space at a minimum. However, there is a lack of research on delivering VR learning for the ASD population using VR headsets. In this paper, we report a case study involving four children with ASD, who were recruited to experience the prototype software for VR learning in our laboratory environment. Our observation reveals that the design allows children with ASD comprehend the three dimensional world and interact with virtual objects and avatars smoothly while using the VR headsets.