Due to their brittleness, bulk metallic glasses (BMG) are generally difficult to form at room temperature. Casting of BMG is one way to get components but an alternative route is to use the capacity to reach particularly large strains when the glasses are deformed in their supercooled liquid region (SLR). The experimental window (temperature, time) in which high temperature forming can be carried out is directly related to the glass resistance to crystallization. Such forming windows have been identified for various bulk metallic glasses (mainly zirconium and magnesium based BMG) thanks to compression tests in the supercooled liquid region. The effects of partial crystallization on the high temperature rheologies are also discussed. Finally, forming experiments were carried out in the selected windows.