Peer roles have increased within mental health and alcohol and other drug services. However, there is a lack of understanding about the ‘lived experience’ necessary for success in these roles and how to recruit effectively. This study explores participants’ views on the essential knowledge and skills derived from lived experience to inform the design of peer roles and support effective recruitment. This qualitative study involved 132 participants employed across five multi-disciplinary organizations in the United States. Participants represent three cohorts: designated peer workers, management, and colleagues in other roles. Fourteen focus groups and eight individual interviews were conducted, with separate focus groups for peers, colleagues in non-designated roles, and management. Findings indicate essential aspects of lived experience comprise three domains: life-changing or life-shaping individual experiences (including intersectionality); common impacts of adverse experiences, identification as a peer, and understanding and application of the collective peer thinking and values; and ultimately, Lived Expertise, a unique, experientially developed knowledge base and set of skills that can benefit others. The study identifies Lived Expertise as a unique combination of individual and collectively derived experiential knowledge. Understanding what comprises Lived Expertise can guide the design of roles and improve recruitment strategies, thereby enhancing the effectiveness of roles and support for the peer workforce. This study offers a model for understanding Lived Expertise that can be readily applied in developing recruitment materials, including position descriptions.