Integrated iron and steel plants generate large amounts of metallurgical slag, which usually contains some quantity of metals or mixtures of oxides that could be treated to be recycled in various applications. The conventional method for disposal of slags is dumping. However, it is possible to process the slags to be used in the production of metallic iron, or as an additive in cement making. In this study, a basic oxygen furnace (BOF) steelwork slag obtained from the Kardemir integrated iron and steel works, Karabuk, Turkey is used. A drum magnetic separator system with pre-engineered crucial processing parameters of drum revolution speed, drum radius, drum flesh thickness, and magnitude of the magnetic field applied is utilized, as these parameters have a competing influence on the results. Subsequently, the effects of slag grain size and the drum-blade gap are investigated in the separation efficiency of magnetic grains. It is found that collection of magnetic grains is improved by decreasing the grain size of slags and moreover, the collection of magnetic grains fraction is increased with an increase in the gap between the blades and drum.