The degree of success experienced from counselling interventions to restore employee productivity and improve functioning and well-being raises significant questions from employers and stakeholders. This field study employed a mixed methods design to identify which features of the counselling process mediated the effectiveness of employee assistance programmes and counselling interventions. A total of 449 voluntary participants completed the Clinical Outcomes in Routine Evaluation (CORE) instrument, with additional qualitative data gathered from 7 semi-structured interviews. Data from both studies was combined using a mixed methods approach where progress measured by CORE was linked to client statements of improvement and clients' accounts of therapy were connected with the phased model of progress measured by CORE. The findings suggest structured counselling was effective in enhancing well-being and functioning, and in reducing symptoms/problem severity. The therapeutic relationship was found to be a significant factor in determining success of the process. The results provide organisational stakeholders with evidence to support phased intervention programmes as a viable employee assistance protocol aimed at restoring the functional productivity of valued staff and support for CORE as a measurement tool.