Real-time tracking of moving tumors is one of today's challenges in radiation therapy. This work investigates the tracking performance of VERO, a novel treatment device with gimbaled linear accelerator, especially designed for four dimensional image guided radiotherapy. It is found that the significant impact of organ motion on dose distribution can be overcome by combining a polynomial predictor with a prediction horizon of 50ms with the VERO tracking system. Tracking errors can be reduced from 1.7mm to 0.6mm for realistic patient signals as well as sine wave from 5 to 30 bpm.