This work considers serial production systems with several process steps and a possible quality control at final step. It deals with the problem of optimizing planned lead time when the real lead time for each process is stochastic and the finished product quality is uncertain unless it is inspected. Three analytical models are proposed aiming to minimize the expected total cost, which is composed of the inventory and backlogging costs for the finished product and quality costs associated with inspection and non-conformity. These models correspond to three quality control policies: i) without quality control, ii) with quality control but without taking into account the inspection duration when optimizing the planned lead time and iii) with quality control and with considering the inspection duration when optimizing the planned lead time. Based on the results, it can be highlighted the economic advantage of integrating quality control at the early stage of supply and production planning decisions for some cost parameters conditions. The robustness of the proposed models is also analyzed regarding the variance of the probability distributions of the lead times.