The rapid development of vehicular communications realizes new types of network services for automotive use. Since vehicles are capable of high mobility, it is difficult to keep stable and reliable network connections between vehicles. Regarding multimedia streaming services, a vehicle may not have enough bandwidth to receive good enough quality using a single 3G/3.5G wireless interface. This paper is motivated to let vehicles form a fleet and then investigate the cooperative streaming scenario in a fleet-based vehicular network. When a vehicle requests a video stream from the Internet using its 3G/3.5G connection, it asks neighboring vehicles belonging to the same fleet to download the requested video data cooperatively through these neighboring vehicles' 3G/3.5G connections and then forward these downloaded video to the requested vehicle through V2V DSRC networks. Since the topology of a vehicular network may change dynamically, two video assignment algorithms are utilized to schedule the downloading process among several neighboring vehicles. Then, in the simulation, we observe and investigate the performance of both algorithms. According to our simulation results, the priority-first video assignment algorithm has better performance than the decoding-first video assignment algorithm.