This paper is based on the master's thesis of the first author. Objectives: The purpose of the study is to examine the ability of expository summarization for second, fourth and sixth graders. Specifically, this study focused on macrostructure and microstructure in two expository discourse types (i.e., compare-contrast and cause-effect structure). Methods: A total of 45 students from three grade groups participated. All participants had no problems in intelligence, language, and reading. After participants read two expository discourses, they were asked to fill in the graphic organizers, and to summarize the texts verbally using graphic organizers. Analyses of oral summaries included overall organization, with coherence as macrostructure and language markers as microstructure. In order to examine differences between the three grade groups in each expository discourse, a one-way ANOVA was used. Results: There were significant differences between groups on summarizing two expository discourses, showing that organization, coherence, and language markers significantly increased as students got older. In particular, all three groups were different with each other in regards to coherence. Conclusion: The results showed that as students got older, their summarizing skills developed. That is, students have the ability to be aware of text structure, integrate the incoming information with one's background knowledge, identify main ideas and supporting ideas, and produce sophisticated vocabularies and complex syntactic structures. Summarizing expository discourse would be one effective way to evaluate and intervene with school-aged children because it provides knowledge of macrostructure and microstructure in expository discourses.