While much progress has been made on the technical design and development of digital libraries, much less is known about how and why education digital library content and associated tools can support and enhance the activities of educators in their professional work. This article elaborates a conceptual framework that characterizes teachers' practices when using online learning resources (called 'teaching as design'), and a professional development model aimed at increasing teachers' capacity for designing learning activities in the context of authentic practice. Findings from two workshop implementations showed positive impacts on teachers' knowledge, attitudes, and subsequent behaviours using online learning resources. An analysis of teacher created activities indicates a relationship between the form of design (offload, adaptation, or improvisation) and the granularity of the learning objects utilized in the activity.