In this investigation, the aim was to assess the impact of the interaction between two types of blog post characteristics and the group size on developing critical thinking skills in online discussion. This study was exploratory and interpretative in nature, for this purpose a collaborative learning environment based on educational blogs was designed according to international standards. The methodological approach taken in this study is a mixed methodology based on descriptive and the semi-experimental approach. The study sample was divided into four groups namely, Group (A) was interacted through “separate blogs with detailed comments", and group (B) was interacted through “sequential blogs with detailed comments", while group (C) interacted through “separate blogs with concise comments", and group (D) interacted through “sequential blogs with concise comments". The most obvious finding to emerge from the analysis was that critical thinking skills have been developed in groups A, B, and C. However, the results of this study did not show any significant improvement in group D. The findings of this study have a number of important implications for future practice.