Operation Support System (OSS) operates on 24x7 basis managing Fault, Configuration, Accounting, Performance and Security operations from various Network Elements in a VoIP network. In traditional telephony systems there was a single point of connection from the OSS to the switch. Today VoIP networks are multi-vendor based distributed systems handling voice, data and multimedia content with multiple network elements and element management systems. Service providers expect a carrier grade quality system with single interface from OSS and a transparent flow through configuration management and provisioning system in VoIP networks. The challenge to network vendors and OSS service providers is to provide and end-to-end intelligent flow-through provisioning system across the various network elements and management systems. This paper describes practical tested architecture principles, design and emerging trends of flow-through provisioning system that is scalable and secure to serve millions of customers in a VoIP network.