Zell, who previously agreed to assume the role of chairman when the deal was complete, also became CEO and made immediate changes to the board of directors and senior management.
He added five directors and named two new executives: Randy Michaels as executive vice president and chief executive officer of Interactive and Broadcasting and Gerald Spector as executive vice president and chief administrative officer.
More changes are coming, he made clear.
"We have a tremendous opportunity to take the great brands of Tribune Company, and the enormous talent within the company, to a new level," Zell said in a prepared statement. "Tribune, along with the newspaper industry, has been mired in its monopolistic origins, and we intend to create a fresh, entrepreneurial culture that is fast and nimble, and which rewards innovation."
Tribune's stock was to cease trading at the market's close on Thursday.
The closing came after Tribune received the final cash installment from the four banks financing the deal JP Morgan Chase & Co., Merrill Lynch & Co., Citigroup Inc. and Bank of America Corp. The lenders had given the deal last-minute scrutiny because of declining conditions at Tribune and in the public markets, but the company cleared all the benchmarks needed to secure financing.
The other obstacle to approval, getting the Federal Communications Commission to clear the way for the deal, was removed Nov. 30.
The swift initial moves by the 66-year-old Zell, a self-described "professional opportunist" who has never before run a media company, confirm his reputation as a no-nonsense manager who doesn't hesitate to shake up the status quo.
He plans to add Jeffrey Berg, Brian Greenspun, William Pate, Maggie Wilderotter and Frank Wood to the board a mix of people with ties to both the media and Zell among them.
Berg, 60, is chairman and CEO of International Creative Management Inc. Greenspun, 61, is chairman and CEO of The Greenspun Corp., president and editor of the Las Vegas Sun newspaper and a "significant investor" with his family in Tribune.
Pate, 44, is chief investment officer of Equity Group Investments, Zell's firm. Wilderotter, 52, is chairman and CEO of Citizens Communications. Wood, 65, is CEO of the venture capital firm Secret Communications and a former lawyer who spent 33 years in the radio broadcasting business.
Two existing board members were re-elected as directors: William Osborn, the chairman and CEO of Northern Trust Corp., and Betsy Holden, a senior adviser to McKinsey & Co. and former co-CEO of Kraft Foods Inc.
No one knows exactly what cutbacks, asset sales or other moves to expect from the fiery Zell known as a brilliant investor and bargain-hunter in industries other than media. But even a man who long ago dubbed himself "The Grave Dancer" for his ability to revive moribund properties faces a tough task in trying to turn around the nation's second-largest newspaper publisher, its revenues still in free fall.
A first task, while eyeing other assets, is likely to be to push ahead with auctioning off the Chicago Cubs, whose sale he insisted on as a condition of the transaction.
Under terms set when he crafted the buyout deal in April, Zell's investment in Tribune now rises to $315 million $250 million and he owns warrants to buy about 40 percent of the company, which will be formally owned by an employee stock ownership plan.
Setting the stage for the transition, the company said Wednesday that Dennis FitzSimons would step down as chairman and CEO when the deal closed and will leave the company at the end of the year.
FitzSimons, whose five-year tenure coincided with a historic downturn in the newspaper industry that forced the company's sale, expressed optimism for Tribune's future and hope that the shifting of its resources to focus on the Internet will pay off.
He cited as strengths the recent performance of the TV group, cable superstation WGN, and the company's sizable stakes in the Food Network and the CareerBuilder online classified advertising venture.
Any of those assets could be candidates for Zell to dispose of to raise cash, along with the Cubs, Wrigley Field and the Chicago-based Comcast sports channel, which are targeted to be sold in the first half of 2008.
Tribune owns the Chicago Tribune, the Los Angeles Times and seven other daily newspapers along with 23 television stations and the Cubs.