The Englishman, who posted a 67, is two shots clear of Swede Alex Noren and South African Charl Schwartzel with Northern Irish duo Graeme McDowell and GarethMaybin a further shot adrift.
McDowell's Northern Irish compatriot GarethMaybin will join him in the weekend's final rounds having made the cut on the number at seven over thanks to an eagle at the 18th to close his second round.
Dredge joined Irishman Shane Lowry, GarethMaybin of Northern Ireland, Dane Thomas Bjorn, Spaniards Jose Manuel Lara and Ignacio Garrido, Tano Goya of Argentina and Scots Andrew Coltart and Montgomerie, theEuropean Ryder Cup captain, in qualifying outright at international final qualifying.