Outcomes-based teaching and learning (OBTL) has emerged as one of the useful pedagogical approaches and is widely adopted in countries such as Hong Kong and the Philippines. However, it has been observed that many classroom teachers struggle in faithfully implementing it because of the lack of a tool that would provide rich feedback regarding its implementation. Hence, the current study sought to develop and validate an instrument that will assess in-service teachers' implementation of OBTL in the classroom. This paper describes the assessment instrument development process and results from 903 university students. Results provided strong empirical support for the six OBTL domains (i.e., learning process, instructional strategies, assessment, learning environment, classroom management, and teacher qualities). The items indicated in the assessment instrument were grounded in previous literature about OBTL, with each domain strongly correlating with each other. Implications for classroom practise and future studies are discussed.