Fidelity Investments' Magellan mutual fund appeared to significantly boost its stake in Bank of America Corp. (BAC) in May while it added to its Goldman Sachs Group Inc. (GS) position, according to new records released by the mutual-fund giant.

The fund - a one-time industry bellwether that lost some luster last year amid backfiring financial bets - also boosted its holdings in Wells Fargo & Co. (WFC) last month, according to Fidelity's data.

The $22.4-billion Magellan fund has gone back and forth with Bank of America over the last several months. It significantly boosted its stake in the bank last September, for example, then substantially reduced its holdings of the bank months later.

More recently, Magellan has jumped back in. At the end of May, the market value of the fund's stake in Bank of America was $398.6 million, according to the new Fidelity records, making the bank the fund's tenth-largest holding. The value is up more than eight-fold from the amount reported for the end of April.

The bank's stock price rose 26.2% in May, indicating Magellan manager Harry Lange bought at an opportune time. The stock price has climbed further in June.

Goldman was already a big Magellan holding at the end of April, when it was the ninth-largest company in the fund. Goldman moved up to the number six spot in May, though, as the rise in market value climbed nearly 35% to $475 million. Because the stock rose 12.5% on the month, the sharper rise in market value indicates a beefed-up position in the bank.

Among other financial holdings, the value of Magellan's stake in Wells Fargo rose 80% to $349.4 million at the end of May compared with the end of April. The stock rose 27.4% last month, also indicating an expanded position.

The value of Magellan's large stake in JP Morgan Chase & Co. (JPM) also rose in May, but at the same pace as the stock's nearly 12% climb during the month, indicating the holding didn't change.

Bad financial bets at Magellan, combined with poor-performing technology stocks, contributed to a brutal 2008, when the fund's total return was a negative 49.4%. That poor showing was significantly worse than the broader market's slide. But the fund has done much better than the broader market so far this year, with its total return at a positive 16.3% through Friday, according to Morningstar.com, compared to a barely positive return for the S&P 500.

Morningstar.com rates the Magellan fund with two out of a possible five stars; Morningstar's ratings measure historical risk and return for a fund.

Elsewhere in the fund's major holdings, Corning Inc. (GLW) overtook the top spot from Nokia Corp. (NOK) in May. The fund appeared to trim its large stake in General Electric Co. (GE), while it left its Apple Inc. (AAPL) stake unchanged.

-By Jon Kamp, Dow Jones Newswires; 617-654-6728; jon.kamp@dowjones.com