Research-based assessment instruments (RBAIs) are essential tools to measure aspects of student learning and improve pedagogical practice. RBAIs are designed to measure constructs related to a well-defined learning goal. However, relatively few RBAIs exist that are suitable for the specific learning goals of upper-division physics lab courses. One such learning goal is modeling, the process of constructing, testing, and refining models of physical and measurement systems. Here, we describe the creation of one component of an RBAI to measure proficiency with modeling. The RBAI is called the Modeling Assessment for Physics Laboratory Experiments (MAPLE). For use with large numbers of students, MAPLE must be scalable, which includes not requiring impractical amounts of labor to analyze its data as is often the case with large free-response assessments. We, therefore, use the coupled multiple response (CMR) format, from which data can be analyzed by a computer, to create items for measuring student reasoning in this component of MAPLE.We describe the process we used to create a set of CMR items for MAPLE, provide an example of this process for an item, and lay out an argument for construct validity of the resulting items based on our process.