The Oakland Raiders on Tuesday evening hired Dennis Allen to be their head coach, according to an NFL source, taking him away from the Broncos.

John Fox brought his entire coaching staff to the Senior Bowl Monday and now Fox will return to Denver one defensive coordinator shy of a load.

Allen informed the Broncos he had formally been offered and accepted the job Tuesday night at Senior Bowl preparations.

Allen had met with Raiders general manager Reggie McKenzie earlier in the evening. It was Allen’s second interview with McKenzie.

Multiple league sources also said Tuesday the Raiders had postponed an interview with Bears offensive coordinator Mike Tice before meeting with Allen and had informed Eagles offensive coordinator Marty Mornhinweg he was no longer a candidate as they zeroed in on the the 39-year-old Allen.

Allen’s departure means the Broncos will enter the 2012 season with their seventh defensive coordinator in the last seven seasons. Linebackers coach Richard Smith, a former defensive coordinator with the Houston Texans and the Dolphins would be the team’s in-house candidate to replace Allen. Fox also likely would look at one of his former defensive coordinators in Carolina – former Jaguars head coach Jack Del Rio. Del Rio was fired in November.

Allen improved the Broncos defense from 2010’s dismal performance that saw the team finish at, or near, the bottom of the league’s rankings in every major defensive category, including points, yards allowed per game and sacks. The Broncos finished 20th in yards allowed per game this season (357.8), 24th in points allowed per game (24.4) and tied for 10th in sacks (41).

McKenzie first interviewed Allen last Tuesday in Denver.

Jeff Legwold: jlegwold@denverpost.com