This study investigated the effects of instruction based on a SCOBA—a schema for a complete orienting basis of an action—on young EFL learners’ understanding of English noun countability. A total of 81 third-grade elementary school students were assigned to either a SCOBA-based or a picture-based instruction group. Over four weeks, both groups practiced target nouns using pictures, but the SCOBA-based group additionally used a SCOBA, a mediational tool in concept-based language instruction (C-BLI). Although both groups showed comparable achievement on the immediate posttest, the SCOBA-based group significantly outperformed the picture-based group on the delayed transfer test involving novel nouns. Qualitative analysis of post-intervention surveys revealed that the picture-based group relied mainly on rule-based explanations, whereas the SCOBA-based group more often drew on concept-based and property-based explanations. The findings suggest that picture-based instruction may help young learners recognize recently taught noun forms; however, SCOBA-based instruction may be more effective in promoting a transferable understanding of English noun countability.