The present study used a focus group methodology to qualitatively explore elementary writing teachers' attitudes and experiences using an automated writing evaluation (AWE) system called MI Write as part of a districtwide implementation of MI Write in Grades 3-5 in 14 elementary schools. We used activity theory as a theoretical framework to answer the following research questions: In what ways do teachers perceive AWE to mediate their own, and their students', activity in the elementary writing classroom? How, and in what ways, do teachers perceive AWE to transform the teaching and learning of writing? Using an inductive coding method, four themes emerged that highlight the complexities of using AWE to support instruction: (1) AWE both assists and challenges teachers; (2) AWE influences students' writing motivation and independence in complex ways; (3) AWE functionality may create new instructional challenges; (4) AWE implementation and efficacy is influenced by broader aspects of the instructional activity system. Findings have implications for informing district and school stakeholders interested in the use of AWE to support writing outcomes advancing research on AWE, for guiding future research, and for guiding the design of AWE systems. [This article was published in "Computers & Education" v168 Article 104208 2021.]