Quality of Service (QoS) is crucial for certain applications such as multimedia. As the Object-based Storage Device (OSD) protocol emerges as the next generation storage technology, QoS provisioning for OSD-based systems has also received a great deal of attention. In this paper, we propose a QoS framework for OSD-based storage system that integrates both the network QoS and storage QoS. We examine the existing OSD specification and analyze the QoS requirements for applications on OSD clients. Based on the QoS requirements analysis, we propose a three-level QoS specification. We further elaborate on extensions to the existing OSD and iSCSI protocol to support our QoS specification. These extensions are then incorporated with the current OSD reference implementation. Finally, we discuss both the implementation structure and issues encountered as part of this study.