This study examines strategies for supporting vocabulary and content learning in 5 grade 9 Earth Science classes that are part of a SDAIE program (Specially Designed Academic Instruction in English) in an urban California high school. Students received vocabulary and content instruction during a unit on Earthquakes. One group of students performed rational cloze (gap-filling) exercises as a postinstruction activity, while a second group performed reading comprehension exercises. In immediate and delayed posttests, the 2 groups showed no differences in receptive learning of vocabulary and content. However, in delayed posttests, students in the rational cloze group performed better on paragraph summary writing using content-area vocabulary and expressing content knowledge. Their superior performance may be attributable to 2 factors: The rational cloze activity gave them opportunities for text rehearsal (i.e., reading and understanding the passages while filling gaps) and the rational cloze passages gave them discourse-level language models. In a follow-up questionnaire, students in the reading comprehension group characterized their activity as equally useful to other instructional activities. However, students in the rational cloze group characterized their activity as distinctively more useful than all other instructional activities. Thus, rational cloze activities appear to provide learners with useful scaffolding for vocabulary use and summary writing.