RFID promises to revolutionize the process of identifying, tracking, and monitoring physical objects. Additionally, RFID integration with wireless sensor networks helps both in terms of scalability and low cost of networks. However, redundancies in RFID data occur due to two reasons: the methods needed to counteract the unreliable nature of radio frequency transmissions and read tags in overlapping reading ranges in RFID systems. Such redundancies increase network delay and consume limited resources of the network unnecessarily. This problem is recognized as a critical issue in RFID. To resolve this problem, we propose an efficient in-network redundancy filtering (EIRF) method in RFID-capable object tracking systems. Simulation results show that EIRF reduces network delay and processing time in filtering, while eliminating considerable amount of redundant data.