The 4Ms Framework is the foundation of the Age-Friendly Health System (AFHS) movement. While the framework is based on standalone evidence for each M, there is limited evidence about the impact on outcomes when practiced as a set. A composite measure capturing adherence to the many care processes that comprise the 4Ms is a necessary but complex component of closing the evidence gap. We offer a navigation guide that addresses key considerations for developing a hospital-based composite measure of 4Ms care. The Institute for Healthcare Improvement operationalizes the 4Ms Framework as a minimum set of Assessment and Act On care processes. In developing a composite measure of inpatient 4Ms adherence, we offer a 4 step framework with associated discussion of considerations related to composite measure type (eg, continuous, dichotomous), and synchrony within and across the Ms containing these care processes. Using real-world electronic health record data capturing care process adherence in the 4Ms implementation at a large academic hospital, we illustrate the considerations, and report the implications for sample size and composite measure scoring. We also present our selected composite measure-a dichotomous measure delineating 4Ms care when all encounter-level processes (those needing to be done only once during the hospital encounter) are followed and all day- and shift-level processes are followed for at least 50% of hospital days. While there is no single, standard approach to create a 4Ms composite at this early stage of the AFHS movement, as organizations develop their measure(s), our guide and the considerations we suggest should serve to inform this process and support progress toward meaningful measurement.