Olefin epoxidation by [γ-SiW10O36(PhPO)2]4- and H2O2occurs in hydrophobic ionic liquids (ILs), with yields andselectivity up to >99%. The catalytic IL phase is recyclable.Under MW irradiation the reaction occurs with up to 200turnovers per minute. Simultaneous cooling is instrumentalfor quantitative H2O2 conversion.