Engagement can be described as students' tendency to work productively, think deeply, enjoy and value their learning, and to support each other in the process of learning (ZDM article). Each of these dimensions can be indexed by a variety of psychologically validated constructs such as interest and enjoyment, self-regulation, effort, emotional valence and object. The purpose of this paper is to describe a method of assessment that takes under 5 minutes to administer as students are learning mathematics concepts or shortly thereafter in the context of classroom observation and analysis of practices that may support productive engagement. A description of an online survey, its development and psychometric properties assessed in a study of over 1,000 secondary mathematics students in the US is presented, and implications for research on task-level engagement in mathematics classrooms is discussed. [For the complete proceedings, see ED658295.]