The endeavor for operational excellence in the operating room (OR) department is hampered by the uncertainty underlying the patient demand for healthcare resources. Incorporating this uncertainty is complicated since the planning and scheduling decisions involving both resources and patients are typically organized according to a hierarchical decision structure due to the different nature and time horizons of the involved decisions in different phases. Via this research proposal, we aim to link the strategic, tactical and operational decision-making in the OR department and study the impact of policy decisions to embed flexibility in the OR planning and scheduling processes to improve the operational outcome, making the trade-off between efficiency (reflected by OR utilization) and consistency (reflected by the number of schedule changes). More specifically, we aim to give insight in (1) new OR planning and scheduling models, guided by real-life, in order to make a proper transition from higher-level decisions towards coherent operational decisions; (2) an integrated planning and scheduling framework that adequately interrelates the objectives and constraints of the different stages; (3) the drivers of the operational performance and the impact of different policy decisions introducing flexibility in some stage of the OR planning and scheduling process to increase the schedule responsiveness to unforeseen operational variability.