The Bears also interviewed their own special-teams coach, Dave Toub, on Monday, according to a source.
After an unsuccessful stint as coach of the San Francisco 49ers, Singletary was hired by his former Bears teammate Frazier to be a linebackers coach and a special assistant. He's been with the Vikings for two years.
Priefer has completed two seasons as special teams coordinator, helping steer the organization's decision to cut veteran kicker Ryan Longwell and draft Blair Walsh, who made the Pro Bowl as a rookie this year.
Chicago, which is looking to replace the recently fired Lovie Smith, stayed in-house Monday to interview Toub, who interviewed for the Miami Dolphins' head-coaching vacancy last season. An original member of Smith's staff who joined the Bears organization in 2004, Toub has molded the club's special-teams unit into one of the top outfits in the league over the past nine years. The Bears had the No. 1-rated special teams in 2006 and 2007 and are annually ranked in the top third of the league.
Messages to Toub's agent looking for a comment went unreturned. The Chicago Tribune reported the Toub interview earlier Tuesday.
The Bears also were scheduled to interview Marc Trestman, coach of the CFL's Montreal Alouettes, on Monday.
The Bears also have been given permission to interview Houston Texans offensive coordinator Rick Dennison, a source told ESPN NFL Insider Adam Schefter on Sunday.
Chicago also received permission to speak to Seattle Seahawks offensive coordinator Darrell Bevell, sources confirmed to ESPN on Sunday.
ESPNChicago.com's Jeff Dickerson and The Associated Press contributed to this report.