To ensure a successful transfer of messages in Vehicular Ad hoc Networks (VANETs), data communication channels between vehicles must meet specific standards. As a result, determining the Quality of Service (QoS) of the communication links established among vehicles is a critical task. In this paper, we present a Fuzzy System for Assessment of Quality of Service (FSAQoS), in which we consider two models (FSAQoS1 and FSAQoS2) to assess QoS in Software-Defined VANETs (SDN-VANETs). FSAQoS1 takes into consideration the latency of message transmission between neighboring vehicles, the reliability of data exchange, as well as the beacon signals disseminated across the network that inform vehicles about the state and location of their neighbors. In addition to these parameters, FSAQoS2 considers the interference of the concurrent transmission of nearby vehicles. We evaluate the proposed system by computer simulations. From the evaluation results, we see that FSAQoS2 shows better results than FSAQoS1, although its complexity is higher.