Chris Wisler carded a 66, to tie the course record, and to join Clint Jensen (67) in a tie for second at 6-under-par 138.
Jeff Cuzzort, who owned a share of the first-round lead in his first professional event, stumbled to a 1-over 73 to drop to minus-5. Bryan Conway also shot 67 to move into fifth place at 4-under-par 140.
Oppenheim opened his round on the 10th tee and parred his first three holes. He then dropped in back-to-back birdies from the par-3 13th to move to minus-4.
The 24-year-old Oppenheim birdied the par-5 17th at Wild Bluff Golf Course for the second straight day. Around the turn, he converted a birdie try at the first to get to 6 under.
Oppenheim, who is looking for his first Canadian Tour win, dropped in his fifth birdie at the par-4 fifth. He stumbled to his lone birdie at the par-3 eighth. He atoned for that error with a two-putt birdie at the par-5 ninth to gain the overnight lead.
'I made some big putts today that allowed me to keep the round going and to take it low,' said Oppenheim. 'There is a lot of trouble on that course, so I'm pretty relieved to get out of there in good shape.'
Dirk Ayers, who shared the first round lead with Cuzzort, faltered to a 3-over 75. He shares sixth place with Derek Gillespie at 3-under-par 141. Tiziani, Ben Ferguson, Brad Fritsch and Wes Heffernan are one stroke further back at minus-2.
At stake this week is an exemption into the second stage of the three-tiered PGA Tour Qualifying school later this fall. The top two on the Canadian Tour money list earn that exemption. Erik Compton currently owns the top spot on the money list with David Hearn in fourth place. Both of those players are competing in this week's Nationwide Tour event in Utah.
Brad Sutterfield stands in third place on the money list and made the cut at even-par 144. Stephen Woodard, who stands second on the money list, survived the cut by one stroke at plus-2.
A total of 67 players made the cut, which fell at 3-over-par 147, for the weekend.