Fraction proficiency continues to be a challenge for many learners of mathematics. Valid and reliable methods for assessing fraction understanding are critical tools in the pursuit of meeting this challenge. Written assessments have been widely used with K-12 students to assess fraction understanding, including units coordination. However, using these types of assessments with a preservice PreK-8 teacher population has proved difficult and inconclusive. Preservice PreK-8 teachers have a variety of algorithmic techniques at their disposal, which has resulted in the need to reexamine how units coordination is assessed in this population. This paper shares the subsequent reconceptualization of assessing preservice PreK-8 teachers' units coordination. [For the complete proceedings, see ED630060.]