Teachers experience difficulty demonstrating prediction strategies and leading discussions in traditional classrooms. It is also unclear whether online discussion can contribute to reading comprehension. The purpose of this study is to create an online reading system to investigate whether learners can acquire reading strategies and enhance their reading comprehension through online discussion. Because students who are simultaneously immersed in two learning practices may experience cognitive overload, this combined strategy instruction system was compared to single strategy instruction systems that allow only one learning practice at a time, either prediction or discussion. A total of 110 5th-grade students participated in this study. The results revealed that single strategy instruction was more beneficial to students' reading comprehension, and the reasons combined strategy instruction was less efficient are discussed. Students' prediction types and the quality of discussion between the two instructions were also reported.