A full-scope simulation study with licensed nuclear power plant operators was conducted to evaluate whether displays designed using Ecological Interface Design (EID) could support improved Situation Awareness over traditional displays. EID demonstrated performance advantages over traditional displays in beyond-design basis scenarios where operators were unable to rely on procedures. The same effects were not seen in within-design basis scenarios where procedures were available. This suggests that EID has the potential to improve SA in unanticipated situations, but that ecological interfaces should be supported with task-based displays in procedure-driven situations.