This study implemented differentiated instruction (DI) featuring tiered tasks and heterogeneous grouping tasks in three mixed-level English classes at a military institution in Taiwan, a setting that is small, admits students with varying English proficiency levels, and is culturally cohesive. The end-of-semester student survey and interview show that the students appreciated the opportunity to choose among various kinds of activities in accordance with their levels and benefitted from cooperative learning. The qualitative data also show evidence that their classroom behaviours were aligned with the militarized culture's values of group solidarity, hierarchical teamwork, and competitive striving. The results support further study into how cultural orientation can be used in planning DI activities for a military or other similar settings.