The two-time U.S. Open champion totaled 17-under 199 at Golfclub Munchen Eichenried. Goosen hasnt won on the European Tour since early 2007.
Bernhard Langer of Germany (65) is second. Nick Dougherty of England (68) and David Drysdale of Scotland (68) are at 202.
Goosen, the leader throughout the tournament, extended his advantage to four strokes at one point. He had three birdies on his first five holes.
Langer, seven weeks short of his 52nd birthday, is bidding to become the oldest player to record a victory on the European Tour since it was launched in 1972. The record is held by Des Smyth of Ireland, who was 48 years and 34 days old when he won the Madeira Island Open in 2001.
Langer has never won this tournament in his home country in 18 previous attempts.
Colin Montgomerie extended his European Tour record for holes-in-one to nine after nailing the 156-yard 8th hole.
The only decent shot I hit all day, he said.
The European Ryder Cup captain shot 72 and trails by 14 strokes.