Teleost fishes are a highly diverse and ecologically essential group of aquatic vertebrates and include coho salmon, Onchorhynchus kisutch. Coho are semelparous and all ovarian follicles develop synchronously. Owing to their ubiquitous distribution, teleost provide critical sources of food worldwide through subsistence, commercial fisheries, and aquaculture. Enhancement of commercial hatchery practices requires a detailed knowledge of teleost reproductive physiology. Despite decades of research on teleost reproductive processes, an in-depth proteome of teleost ovarian development has yet to be generated. We describe a coho salmon ovarian proteome of over 5700 proteins, generated with data independent acquisition, revealing the suite of detectable proteins that change through the transition from primary to secondary ovarian follicle development. This transition is critical for puberty onset, egg quality, and further embryonic development. Primary ovarian follicle development was marked by differential abundances of proteins involved in carbohydrate metabolism, protein turnover, and the complement pathway, suggesting elevated metabolism as the oocytes enter maturation. The greatest proteomic shift occurred during the transition from primary to secondary follicle growth, with increased abundance of proteins underlying cortical alveoli formation, extracellular matrix reorganization, iron binding, and cell-cell signaling. This work provides a foundation for identifying biomarkers of salmon oocyte stage and quality.