For the past five years, colleagues in the Strategic Literacy Initiative at WestEd have been designing and implementing a professional development program focused on enabling teachers to build their understanding of the complexities of reading. In developing this program, centered around what they call a "Reading Apprenticeship" framework, the Initiative has been working collaboratively with cross-school networks of interdisciplinary site-based teams involving over 300 middle and high school content area teachers throughout the San Francisco Bay area. The goal for these professional development sessions is to assist teachers in building the internalized knowledge and experience base necessary for them to carry out the kind of long-range planning, refinement, and on-the-spot classroom problem-solving that expert teaching of reading within a content classroom demands. Rather than a professional development approach, the approach being developed is what is called a "generative model." It is generative in the sense that teachers engage in a series of highly-designed activities over time intended to challenge their conceptions of reading tasks and perceptions of students' reading, and to expand their knowledge from which they can then generate various solutions to assist students' reading development in their classroom. The center of the program is a guided and carefully structured inquiry process, or cycle of inquiry, built around what is called literacy learning cases. For the past three years, a study of teacher knowledge growth and change in the professional development networks has been carried out, and the program's case inquiry method appears to help teachers teaching content reading. Contains 20 references. (NKA)