United States Forces Korea (USFK) personnel represent a distinctive group of Korean language learners whose opportunities for spontaneous Korean interaction may be limited by the English-dominant environment of military bases. Although Korean instruction for USFK learners has often focused on test-oriented linguistic knowledge, learners may also need to understand how language choices function within everyday interactions. This exploratory study proposes a genre grammar-based framework for organising Korean language instruction for USFK learners, using shop interaction as a case. The framework was developed from the researcher’s experience teaching Korean to USFK learners, informal conversations with four learners at Camp Humphreys, and existing instructional materials and research. The learner conversations were conducted naturally during instruction and were used as contextual information rather than as a systematic qualitative dataset. Drawing on genre grammar and functional approaches to language, the study organises shop interaction through four interconnected levels: social purpose, discourse stages, communicative functions, and linguistic resources. Six stages—greeting, exploring, requesting, purchasing, payment, and closing—are proposed, with each stage linked to relevant grammatical, lexical, discourse, and politeness resources. The framework illustrates how commonly taught expressions can be presented in relation to the communicative functions they perform and the stage of interaction in which they occur. Rather than establishing a universal model of shop interaction, the study offers a pedagogical framework for making the relationship between discourse progression and language choice explicit. The framework provides a possible basis for developing genre-based Korean instruction for USFK learners and for extending this approach to other everyday interactional genres.