Grammar Instruction has an important role to play in helping students to speak and write more effectively. The purpose of this study was to examine the effects of direct grammar instruction on the quality of student's writing skills. The participants in this study included 18 fifth grade students and two fifth grade teachers. Based on the results of the students' pre-assessment writing scores through Write Score, direct grammar instruction was administered to address common errors found in their writing. The students receive direct grammar instruction each week for about four months. At the end of the four months the students were given a writing post-assessment. The results indicate that after 4 months of direct grammar instruction half of the students who participated in the study showed significant increases in their overall writing scores. These results show that students can make adequate progress to improve their writing when research based strategies such as grammar instruction is implemented during writing instruction. Educators need to receive more training to increase their knowledge of effective research-based writing strategies in order to improve the overall writing quality of their students.