This paper defines a model of teacher practice ("teaching as design"), and describes a professional development curriculum in which K-12 teachers design learning activities using resources and tools from education digital libraries. It then presents preliminary findings from an application of this model in which teachers' artifacts are analyzed to learn how online learning resources are used in situ. Initial results suggest that learning resources of a smaller granularity are more likely to be adapted or improvised upon in teacher-designed learning activities, which further supports teachers' becoming contributors of online resources and active participants in an education cyberinfrastructure.