When the coliseum sign is raised today on the home field of the Oakland Raiders and Oakland Athletics it will read: O.co Coliseum.

That will be the most visible-to-date marketing sign of the brand's shift from Overstock.com to O.co since the company began the transition earlier this year. The online retailer's website will also change with the logo heading, changing to "O.co, also known as Overstock.com," said CEO Patrick Byrne. TV ads will begin to reflect the change to O.co after Father's Day.

"O.co will keep on emerging as our brand," he said. "It's been a gradual transition. We didn't want to risk throwing out the brand equity we've built with Overstock.com. ... I think if it all works really nicely, you'll just see Overstock.com fade away and O.co take its place."

Overstock President Jonathan Johnson likened the change to when Kentucky Fried Chicken changed its name to KFC. "Our business has changed. We used to be a pure liquidator and our product was all overstock. Now 70% of our product is first-run replenishable goods," he said. "We've been known for a long time as the O. TV commercials back in 2004 used 'It's all about the O.'"

The company said O.co as a brand name also works better globally, whereas the word "overstock" is sometimes difficult to translate. While Overstock has what Mr. Johnson called a "nascent" global footprint, he said it plans to grow significantly and begin to build "in-country" presence overseas.

Not everyone is on board with the O.co idea, however. "They're trying to tie back to something that doesn't have strong brand equity," said William Lozito, president and chief branding officer at Strategic Name Development. "It seems like going from one extreme to the other, and it doesn't seem to be a wise branding approach."

And then there's the matter of the letter itself. "'O' really seems to be owned by Oprah," said Steven Donaldson, principal of Radiant Brands, who was as concerned with that as much as the loss of the Overstock equity. "I'd worry that the women who identify with that might almost be offended by the taking of 'O' from Oprah. Are they diluting their brand with that confusion?"

Mr. Johnson acknowledged Ms. Winfrey, adding President Obama and Oakley sunglasses brand to the well-known O crowd, and said: "But all of those are great brands, and if we get some of their stink, we'll take that ."

Mr. Byrne said the typical feedback from customers and merchants hasn't been dissent, but rather wondering why the change hasn't happened faster. Already 20% of its customers are going directly to the O.co homepage vs. Overstock.com, he said.

The name change has afforded an opportunity to change taglines as well, with O.co now the "savings engine" -- moving away from Overstock.com's "your online outlet."

Overstock bought the stadium naming rights in April but needed to make the change now because the Coliseum sign needed to go up and it wanted to avoid the prohibitive expense of creating two LED signs. The new one goes up just in time to put O.co's red-and-white logos front and center at a U2 concert in the Coliseum on Tuesday night.

Overstock's deal with the Oakland-Alameda County Coliseum is for six years at a reported price tag of $7.2 million. In both 2009 and 2010, the company consistently spent around $27 million in measured media, according to Kantar Media data.

Mr. Donaldson suggested that the new "O" moniker could spark some creative TV and radio advertising. "For TV or radio, it could be hysterical, but they'd really have to take themselves lightly for that to work," he said.

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