A series of seismic tests were conducted on a 1½-bay by 1½-story special steel moment-resisting frame subassembly from the onset of damage through incipient collapse. These tests were conducted using hybrid simulation with substructuring as a mean to demonstrate efficient testing methods for system-level collapse assessment of large-scale structural subassemblies. The ½-scale specimen was designed to capture the behavior and interactions of beams, columns, panel zones, and composite floor slab. The experimental test setup permitted the application of lateral as well as varying vertical forces on the test specimen while maintaining realistic boundary conditions on the subassembly. With the overarching objective to advance knowledge on the collapse assessment of frame structures under earthquake loading, this paper focuses on the seismic performance of a steel moment-resisting frame through collapse. The failure mechanisms of the test frame are described and compared with numerical simulations based on state-of-the-art modeling approaches.