Calcined olivine is a cheap, active material that can be employed as an in-situ catalyst to reduce the tar content of fuel gas produced during air-blown gasification of biomass in a fluidized bed. In the present work, a series of tests were conducted with olivine pre-treated at 1200 °C as a bed material. Pre-treatment improved gas quality compared to non-active bed experiments: hydrogen production increased due to hydrocarbon and tar reforming. In order to determine the physicochemical properties of calcined olivine in terms of tar reforming, temperature programmed reduction (TPR) tests were performed. The material was also characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy combined with Energy Dispersive Spectroscopy (SEM/EDS) before and after its utilization into biomass gasification. Gasification tests involved two biomass species (sunflower and willow) and were conducted in a 100 kWth air-blown, atmospheric pressure, circulating fluidized bed at two different temperatures (750 °C and 800 °C) with three bed materials (silica sand, olivine and calcined olivine).