In 2006, composer James DeMars conceived of an opera when he began setting the Aztec legend known as Nican Mopohua, the “legend of Guadalupe.” Many inherent challenges arose as DeMars began to compose his first opera. His unfamiliarity with operatic writing and production, a preference for the aural elements of opera over visual ones, inexperience with dramatic textual writing, and insecurity in his ability to have it produced, encouraged him to detour from his operatic vision altogether and instead write an oratorio. Yet, his original operatic concept revealed itself through the music and text enough to encourage him and others to believe that his oratorio, Guadalupe: Our Lady of the Roses, could be produced on the operatic stage. Despite the oratorio’s success, DeMars persisted in realizing his original operatic vision and began the arduous task of rewriting his opera in 2012. To overcome the challenges, he relied heavily on the input of an “Operatic Advisory Council.” This group of dedicated colleagues and experts in the field of opera revealed to DeMars certain essential elements of opera that were absent from the oratorio, and through the course of three years advised and instructed the composer as he transformed his oratorio into an opera – something rarely attempted in the operatic repertoire. In this document, Chapter 1 discusses the formation of the Council, its members, and the expertise they offered. Chapter 2 presents the areas of concern the Council had during the process. Chapter 3 discusses the methods by which DeMars rectified the flaws in the oratorio’s visual aspects, the vocal writing, and the dramatic elements that needed attention. It also presents musical and textual examples of the adjustments and additions DeMars made during the transition, and discusses their effect on the opera’s staging, vocal writing and drama. The changes DeMars made under the guidance of the Operatic Advisory Council ultimately resulted in an operatic version of Guadalupe, which premiered at Arizona State University in November 2015.