This paper introduces an innovative approach for designing a downstream oil supply chain network under uncertain conditions, aiming to bridge existing gaps in tactical decision-making and day-to-day operational management. In the initial phase, the focus lies on tactical and operational decisions related to network planning, while the second phase emphasizes real-time transshipment decisions for daily operations. This two-phased strategy proves to be adaptable and proficient in effectively handling uncertainties. Applying the mixed possibilistic-flexible programming and a rolling horizon approach, we enhance the overall performance of the oil supply chain network. To validate the efficacy of our proposed method, we conduct a comprehensive case study utilizing a database sourced from governmental agencies, specifically tailored to the Iranian oil supply chain. Our results demonstrate the efficiency of the proposed approach in addressing uncertainties, including demand fluctuations and network costs. Furthermore, the methodology exhibits potential for broader applications in other supply chain systems and industries grappling with similar challenges.