For many organisms, the earliest life-history stages are both the most sensitive and most difficult to examine. However, because population growth requires successful recruitment, understanding the conditions necessary for embryo and juvenile success is vital for ensuring long-term persistence. To support captive breeding and population recovery of Blunt-nosed Leopard Lizards (Gambelia sila) from the Panoche Plateau we used modern, non-invasive methods to monitor oviductal egg production and estimate environmental conditions suitable for post-oviposition egg development. Prior to oviposition, we monitored egg development via field ultrasonography. These data allowed us to quantify reproductive output, qualitatively describe the phases of egg development, and create a predictive model of time until oviposition based on the size of developing eggs. We then used climate data paired with microclimate modeling to estimate hourly temperatures and water potentials that eggs are expected to experience within natural nests. We used this information to develop a naturalistic egg incubation regime that successfully produced robust hatchlings. These tools could be used to better understand the requirements of the earliest life-history stages in a diverse group of reptiles when direct measurements are not feasible.