Only a few years ago, the holy grail of TV advertising was your beer bottle or soda brand appearing within a TV show, organically (or not so organically) placed in a bar scene or sipped by a panel of judges. Today, the beer or soda might be part of a series of web videos starring TV show talent or part of a social-media contest around a network.

Now that viewers are watching TV shows on their own schedules and on a variety of devices -- often allowing them to completely skip commercials -- agencies, clients and networks are thinking beyond the commercial break with custom content. TV programmers are creating dedicated divisions: Viacom introduced its branded-content arm, Viacom Velocity, in January; CNN's Digital Studios is creating custom content for clients like Cisco; Turner Broadcasting has tapped Funny or Die to create custom content across its divisions; and NBC Universal has its client-solutions group that caters to extending advertisers' media buys with custom content.

The demand has been so robust that several TV networks claim branded content has become part of nearly every ad deal. For Viacom, 90% of its upfront deals included a Velocity component, said Dario Spina, exec VP-integrated marketing. Alison Tarrant, exec VP-client solutions group at NBC Universal, said that custom content is part of nearly all of NBC Universal's ad deals.

"Advertisers are paying a lot of money in a show for their product to be seen, sometimes for just 10 seconds," said Ms. Tarrant. "That's not to say in-show integrations aren't still valuable. There's still a value to having products integrated in an organic way. But advertisers are thinking more about the economics of in-show integrations vs. branded content."

"In the past, the trend was toward in-show integrations or 'brought-to-you-by' segments," said Eric Levin, senior VP-group client director at LiquidThread and head of the content division at Spark. "Now advertisers want to have a deeper presence in shows."

While custom content on TV isn't new, what has changed is the ability for such content to extend beyond the confine of the commercial break. The ability for the content to travel on multiple platforms means it can have a multiplier effect and there's greater potential for long-tail engagement, Ms. Tarrant said.

This makes the distribution conversation around custom content extremely important, and TV networks have been willing to give clients ownership of content so it can be distributed beyond the networks' own channels and sites.

Content marketing is also changing the cycle of TV buying and selling, requiring conversations to start much earlier in the media-planning process, even before budgets are submitted, said Katrina Cukaj, exec VP-ad sales, CNN.

Custom content was traditionally tacked on to the end of the media-buying and -planning process, Mr. Spina said. Now more media agencies are thinking content marketing first, with the creative conversations happening earlier, he said.

Even the players are changing. TV networks are increasingly bringing their creative teams into conversations with agencies' branded-content teams, where in the past those discussions predominantly took place with the network sales team, Mr. Levin said.

And new platforms will only help to push branded content forward. Ms. Tarrant said as video-on-demand becomes a bigger part of media buys the network will be thinking about how to create custom content for the platform.