This report describes the foundation and rationale for a framework designed to measure reading literacy. The aim of the effort is to build an assessment system that reflects current theoretical conceptions of reading and is developmentally sensitive across a prekindergarten to 12th grade student range. The assessment framework is intended to document the aims of the assessment program, define the target constructs to be assessed, and describe the assessment designs that are aligned with the aims and constructs. This framework report is preliminary in that we are engaged in an iterative process of writing and revising the framework, based on what we learn from efforts to instantiate the ideas in new assessment designs and the results we garner from piloting novel designs. We also anticipate drafting further sections to address issues such as the scoring models and analytic plans once assessments have been designed and piloted.