Haas, a 14-time winner on the Champions Tour but without a victory since 2009, made a hole-in-one on the fourth hole of the TPC-Twin Cities course and finished his round with four straight birdies.
Huston is a tour rookie playing in his eighth event.
Peter Senior, Garry Hallberg, Rod Spittle and Tom Lehman, the tour's leading money winner, shared third place at 65. Joey Sindelar, David Eger, Kenny Perry and Mark Calcavecchia were another shot back.
Olin Browne, the winner of last week's U.S. Senior Open, shot a 71. Brad Faxon, a four-time winner on the regular circuit, made his Champions Tour debut and posted a 68. Faxon turned 50 Aug. 1.