The aim of this study is to examine the effect of SCM-based self-regulation writing instruction on the expository writing and self-regulation skills of middle school 7th grade students. In the research, explanatory sequential mixed method, in which qualitative and quantitative research designs are used together, was used. In the quantitative dimension of the study, the quasi-experimental pre-test-post-test paired control group design was used, and in the qualitative dimension, the case study was used. The study group consists of 66 middle school students attending the 7th grade. It was used two quantitative data collection tools in the study. T-test and Covariance (ANCOVA) analysis were used for independent samples to compare the means of pre-test post-test scores. On the other hand, the qualitative data of the study were collected with a semi-structured interview form and analyzed through content analysis. As a result of the findings obtained from the post-test results in the study, it was observed that the expository writing and self-regulated writing skills of the experimental group students were significantly higher compared to the control group students. Qualitative data were grouped under four main themes: motivation, text production, use of strategy, and negativities. [Paper presented at the International Symposium of Limitless Education and Research (3rd, Bodrum, Mugla, Turkey, April 24-27, 2019).]