The exclusion of regular fire and the introduction of livestock grazing have altered native grassland composition on Victoria's volcanic plains, commonly resulting in spear-grass and wallaby-grass pastures replacing Kangaroo Grass grasslands. The effect of reintroducing fire to these pastures is currently unknown, although it may be an important part of restoring this ecosystem. We measured the changes in basal area of the dominant grasses in a mixed Spear-grass/Wallaby-grass pastures after a summer wildfire, which we assume burnt a relatively homogenous grass sward. We found a 90–95% reduction in the basal area of live spear-grass tussocks in burnt plots compared with unburned controls, due to the mortality of tussocks. This suggests that caution and structured experimentation should be applied when using fire to manage spear-grass-dominated grasslands.