A missed approach was executed on the first approach, and the crew elected to fly the complete procedure turn for the ILS at the Central Wisconsin Airport. Both the first and second approaches were flown at 3000 feet MSL in IMC conditions with moderate to heavy rain. A temperature inversion existed from 5000 feet to 3000 feet MSL which created conditions conducive to moderate to severe clear icing. The aircraft was in these conditions for 11.8 minutes. Approximately one-half way through the procedure turn, which was flown with the autopilot on, the captain reduced power to slow for gear extension. At 157 knots clean configuration the aircraft stalled and rolled 80 degrees to the left and 60 degrees to the right. The crew applied full power and executed stall recovery procedures. The aircraft was recovered with an altitude loss of 600 feet. The crew did not perceive any ice accretion, and the airframe deice was not on until after the stall. The third approach was uneventful.