Mr O'Brien, who takes over the top job on October 1, said Australia's biggest supermarket chain would continue to build on its private label range which now included around 2,500 products.
"Our private label range generally increased by some 620 products in this year," he told analysts after the release of the company's full year results on Thursday.
"We've been talking for a number of years about our increased focus on private label.
"It's coming to bear and it's helping with both our sales, our customer loyalty and our margin mix at the end of the day."
As well as the 2,500 private label products at Woolworths, all of the company's businesses, including Dick Smith, Big W and Masters home improvement, have significant additional private label businesses.