By Anupreeta Das And David Benoit 

Major investors made striking bets with their energy holdings in the fourth quarter amid a collapse in the price of oil.

Warren Buffett's Berkshire Hathaway Inc. and George Soros's Soros Fund Management sold off all their shares in Exxon Mobil Corp. as of Dec. 31, while hedge-fund manager John Paulson made a new bet with 70 million shares in Talisman Energy Inc. valued at $549.1 million.

The disclosures were made Tuesday in a regulatory filing required of investors who manage more than $100 million.

Oil prices have plunged from north of $100 a barrel in June to roughly half that level now, the victim of a growing surplus brought on by booming U.S. production and weaker-than-expected demand. The volatility in prices has given investors opportunities to bet on further declines or a sharp rebound.

Berkshire sold about 41 million shares of Exxon, having initially disclosed its ownership of the stock in the third quarter of 2013 and adding to it slightly in later quarters. The nearly $4 billion position made Berkshire one of Exxon's largest shareholders. Exxon, the biggest U.S. oil company, said earlier this month it was looking for ways to cut costs as profit fell during the fourth quarter.

The Omaha, Neb., conglomerate also sold off a small position in ConocoPhillips and cut its stake in National Oilwell Varco Inc., an oil-and-gas drilling- equipment maker, by about 18%. However, it increased stakes in two other energy-sector companies, Phillips 66 and Canadian oil-sands company Suncor Energy Inc.

Mr. Paulson, who made his name during the 2008 financial crisis betting against the housing market, wasn't entirely bullish on energy. He exited from Athalon Energy and pared back his holdings in Oasis Petroleum Inc. even as his ownership of Whiting Petroleum Corp. rose nearly 44% due to its December acquisition of another company where Mr. Paulson had a 26 million-share stake.

Others who took similar steps away from energy include New York hedge fund Jana Partners LLC and David Einhorn's Greenlight Capital Inc., according to filings Tuesday and last Friday.

Greenlight sold out of BP PLC Anadarko Petroleum Corp. and National Oilwell Varco, while Jana Partners exited from stakes in oil-and-gas producer Apache Corp. and other companies where it had been pushing changes. It had called for Apache to sell its international assets and concentrate on drilling in the U.S.

Daniel Loeb's Third Point LLC exited some of its energy holdings even as it also loaded up on other names.

One of its biggest new positions was in refinery company Phillips 66. Third Point held five million shares worth about $359 million as of Dec. 31, according to a regulatory filing. And Third Point also took new positions in Rice Midstream Partners LP and Cobalt International Energy Inc.

"We are looking to add exposure during market dislocations," Third Point said in a letter to investors earlier this month.

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