Outcome harvesting (OH) is a participatory evaluation approach that offers excellent flexibility to measure complex program outcomes, especially where program interventions involve capacity development and institutional behavioral changes among social actors. The PEPFAR/USAID ACHIEVE project adapts OH in its countries of implementation to determine systems strengthening outcomes where traditional quantitative methods fall short of assessing those outcomes. In Zambia, OH is core to ACHIEVE’ s annual learning agenda to identify the interventions’ outcomes, best practices and inform adaptive management. During ACHIEVE Zambia’s implementation in 2022, ACHIEVE encountered OH methodological challenges within five process principles of the method’s nine engagement principles, specifically, related to designing the data collection tool to cover multiple local settings and defining selection criteria of respondents throughout engagement and substantiation. These challenges impacted the data collection process, analysis and reporting and resulted in an incomplete story of the project outcomes from the harvest. In this panel discussion, ACHIEVE will share lessons learned and will facilitate an open discussion on how the analyst addressed the challenges faced with the methodology.