Oosthuizen moved up from seventh, switching places with Adam Scott after a fourth-place finish at the Nedbank Golf Challenge in South Africa.
The only other change in the Top 10 had Brandt Snedeker passing Webb Simpson for ninth place, forcing Simpson to 10th. This despite Simpson finishing seventh and Snedeker in a tie for 13th at the World Challenge event in California
McDowell, who won the World Challenge for the second time in three years, moved from 24th to 14th in the rankings while tournament runner-up Bradley reached No. 11 after starting the week at 15th. Martin Kaymer won the Nedbank Golf Challenge and improved his ranking to No. 28. He was 32nd last week.
Jason Dufner is in eighth with an average of 5.627, with Snedeker at 5.560, just ahead of Simpson's 5.549.