The Evidence-Centered Design (ECD) framework was used to create a special education teacher observation system, Recognizing Effective Special Education Teachers (RESET). Extensive reviews of research informed the domain analysis and modeling stages, and led to the conceptual framework in which effective special education teaching is operationalized as the ability to effectively implement evidence-based practices for students with disabilities. In the assessment implementation stage, four raters evaluated 40 videos and provided evidence to support the scores assigned to teacher performances. An inductive approach was used to analyze the data and to create empirically derived, item level performance descriptors. In the assessment delivery stage, four different raters evaluated the same videos using the fully developed rubric. Many-facet Rasch measurement (MFRM) analyses showed that the item, teacher, lesson and rater facets achieved high psychometric quality. This process can be applied to other content areas to develop teacher observation systems that provide accurate evaluations and feedback to improve instructional practice. [This is the online version of an article published in "Educational Measurement: Issues and Practice."]