The objective of this paper is to provide an optimized low-cost solar oven for the more than 200,000 households (INEC, 2014) using firewood or coal for cooking in the rural sectors of Ecuador coastal zones. According to the Köppen-Geiger classification, those zones are identified as an Aw region (i.e., humid), with abundant cloudiness and high temperatures. Currently, there are a large number of commercial solar ovens showing high performances in vastly irradiated climates. However, its suitability in low to average irradiation areas is doubtful, not to mention the high costs for households at risk of exclusion. Considering the climatic and socioeconomic conditions of the target population, three different oven prototypes have been designed and tested, always under real sun conditions. The technology has been adapted to be constructed with low-cost local materials of easy access for the inhabitants even those of remote areas. The effect of the construction components, simple and complex reflection plates and thermal storage has been evaluated. For this, internal and external temperature data, solar irradiation, cooking time and thermal inertia have been monitored and analyzed. The thermal losses have been evaluated using thermographic images. The performance of the proposed prototypes has been compared with the response of the most common commercial ovens. The results were promising in relation to the food cooking time, lower energy losses by using insulating materials, thermal stability and heat accumulation for a longer time in comparison with the current commercial products.