This article describes nine phases of curriculum-development activities conducted by the Language and Reading Research Consortium (LARRC), the end result of which was to arrive at a research-based supplemental curriculum that could be used by teachers of English-speaking or bilingual Spanish-English-speaking children in prekindergarten and English-speaking children in kindergarten to third grade to bring about significant changes in students' language skills as a route to improved reading comprehension. LARRC followed the Curriculum Research Framework (CRF) proposed by Douglas Clements as a means for developing curricula that can be called research-based; CRF phases include establishing the foundations of the curriculum (Phases 1-4), establishing the learning model (Phase 5), and evaluation of the curriculum and its components (Phases 6-10). This description of the iterative process followed by LARRC provides the educational field with a substantive example of how research-based curricula in reading comprehension and other areas can be developed using the CRF. [This article was written by members of the Language and Reading Research Consortium.]