Operating room (OR) is among the most capital-intensive resources in health systems, yet inefficiencies persist in allocating outpatient surgery across facility types. Although ambulatory surgery centers (ASCs) are optimized for lower-acuity procedures, many eligible cases remain scheduled in higher-cost main hospital ORs, consuming prime-time capacity needed for emergent, complex, or inpatient surgeries and contributing to access delays. This study proposes a greedy first-fit scheduling heuristic to identify outpatient surgical cases eligible for transfer from the main OR and assign them to available ASC OR time slots. The approach is evaluated retrospectively using ten months of fiscal year 2025 EHR-derived surgical data from a pediatric health system with eight main ORs and four ASC ORs. Across the study period, the algorithm identified 2,071 movable outpatient cases and reassigned each without creating scheduling conflicts. Simulated reallocation increased aggregate ASC block utilization from 50.2% to 73.1% across the four ASC rooms, with room-level gains of 18.1–30.8%. These findings demonstrate that the proposed heuristic can serve as a prospective decision-support tool for optimizing surgical case allocation between the main OR and ASC. The algorithm is currently being used prospectively to support future scheduling decisions.