Every quarter many money managers have to disclose what they've bought and sold. Their latest moves can shine a bright light on smart stock picks.

Today let's look at Viking Global Investors, founded in 1999 by Andreas Halvorsen and David Ott, who had previously worked together at Julian Robertson's respected Tiger Management firm. Viking is known as a long-short global equity fund, meaning that it aims to maintain long positions in companies on which it's bullish, and short positions in those where it's bearish.

Viking's stock portfolio totaled $12.2 billion in value as of March 31, 2012, with 57 holdings. The top three holdings, representing 17% of Viking's total value, were Cisco Systems, Google, and Invesco.

Interesting developments
So what does Viking's latest quarterly 13F filing tell us? Here are a few interesting details:

New holdings include Hartford Financial Group (NYSE: HIG) and Las Vegas Sands (NYSE: LVS). Hartford Financial is looking attractive on a purely valuation-oriented basis, with a forward P/E ratio below 5 and a PEG ratio of just 0.4. Its business operations have offered some disappointments, though. Activist investor John Paulson had been agitating for the company to split in two, but he has stepped back from that position, as the company changes its focus some -- by cutting back on annuities, for example.

Las Vegas Sands stock hit a 52-week high last month on elevated expectations for its Singapore and Macau operations. It has been expanding in Macau, where gambling revenue rose 40% between 2010 and 2011, and it's aiming to open a massive EuroVegas property in Spain, as well.

Among holdings in which Viking Global increased its stake was Oncothyreon (Nasdaq: ONTY). It more than doubled in 2011, partly on excitement over its lung-cancer treatment Stimuvax, but when early trial results were a bit disappointing in March, the stock sank some 40%. That may have been an overreaction, but until the drug is approved and selling well, there is plenty of risk.

Viking Global reduced its stake in lots of companies, including Baidu (Nasdaq: BIDU). China's big search-engine company has a lot of bulls, but some are doubtful about the company's attempt to introduce its own operating system for the mobile market, and the company's growth is slowing.

Finally, Viking Global unloaded several companies, such as Occidental Petroleum (NYSE: OXY). Occidental is the largest operator and oil producer in the promising Permian Basin, and has been investing heavily in its California shale reserves. Some see the company as a good long-term investment, and appreciate that it doesn't have a mountain of debt like some other energy companies.

We should never blindly copy any investor's moves, no matter how talented the investor. But it can be useful to keep an eye on what smart folks are doing, and 13-F forms can be great places to find intriguing candidates for our portfolios.

If you'd like to consider promising oil companies other than Occidental, check out our special free report, "3 Stocks for $100 Oil," which will introduce you to some compelling contenders for your portfolio.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.