Last summer Google introduced Google Partner Select, a service allowing marketers to buy ads in “premium” online video content.

With advertisers pumping money into Web video and automated, or “programmatic” buying practices taking hold, it seemed like a no-brainer for the tech giant.

Now some big-name partners are signing on. Google on Tuesday said 30 media companies and 20 brand advertisers had agreed to transact via the exchange, including CBS Interactive, Fox News, Rodale, PGA Tour, Discovery Communications and Scripps Networks.

Google’s pitch to marketers is that with Google Partner Select they can buy inventory from a host of top video sites, using data for targeting purposes. Implicit in that pitch is that these marketers will avoid the low-quality and fraudulent inventory on other exchanges.

Brands that have initiated campaigns via the exchange include BMW and Allstate, according to Neal Mohan, Google’s vice president of video and display advertising. Mohan said marketers are rapidly embracing buying Web video advertising using more automated, data-driven tactics.

Of course, Google is also going after the TV advertising marketplace by directly selling Web video ad packages on YouTube via a more traditional TV-like approach (that isn’t entirely automated)–a program called Google Preferred. Mohan doesn’t see any conflict between those two trends.