Tseng complete the final eight holes of her second round after play was suspended Friday because of rain.
Tseng birdied three of her final four holes to beat the course record of 65 set in 1994 by Martha Nause and equaled Friday by Katherine Hull of Australia.
Tseng and Ochoa head into the third round Saturday tied at 10 under, two shots ahead of Hull. Nicole Castrale is another stroke back and Annika Sorenstam and Se Ri Pak trail the leaders by four.
Sorenstam completed her second round Saturday with a 71 at the Ottawa Hunt and Golf Club.
Tseng won the LPGA Championship in June.