Broad-stroke approaches to vocabulary teaching in preschool include effective instructional elements, yet may be too ill-structured to affect the vocabulary learning of children experiencing serious delays. Using a formative research approach, this study examines the design potential of a supplemental vocabulary instruction technique that incorporated research-based instructional elements into a highly structured approach. The intervention design was tested for instructional potential and delivery in 12 Early Reading First classrooms over a 3-month period, and compared to a control group of children in like classrooms on effects. Fidelity of implementation was assessed on three levels of teaching staff: coach, teacher, teacher assistant. Pre/postintervention effects were measured using the Peabody Picture Vocabulary Test (PPVT-III) and a curriculum-based decision measure. Debriefings with teaching staff were content analyzed. Results show good fidelity of implementation across roles and strong learning outcomes; children responded well to the technique and made significant gains in their vocabulary (PPVT-III) and substantive gains in receptive and expressive vocabulary on a target set of words (curriculum-based decision measure). Additionally the technique appeared relatively easy to adopt and use routinely in the preschool setting. Although limited to an Early Reading First program setting, the design shows promise as a supplemental vocabulary instruction technique. (Contains 3 figures and 2 tables.)