Berkshire owned about 26.53 million Kinder Morgan shares worth roughly $395.9 million at year end, according to a U.S. Securities and Exchange Commission filing detailing its U.S.-listed stock investments.
Shares of Kinder Morgan rallied in premarket trading Wednesday, rising $1.24, or about 8 percent, to $16.86. They had closed up 66 cents at $15.62 in regular trading.
Berkshire has also been boosting its stake in oil refiner Phillips 66. As of Friday, it had spent $1.08 billion this year on Phillips 66 stock, giving it a 14.3 percent stake.
Kinder Morgan shares have fallen by nearly two-thirds since April as falling oil prices cut into profitability.