Berkshire portfolio managers Todd Combs and Ted Weschler, who each invest about $9 billion, made the investments.
Berkshire's new stake in Apple totaled 9.8 million shares, while the company boosted its shares of IBM by 198,853 to 81.2 million shares. Shares of Apple were up 4 percent in afternoon trading. (Get the latest quote here.)
"I think this is basically an example of how there's a transition going on in Berkshire Hathaway," Vahan Janjigian, chief investment officer of Greenwich Wealth Management, said on CNBC's "Power Lunch" on Monday.
"For years, this company has been run by Buffett and [Charlie] Munger. ... What's going on especially with the Apple investment today is that Weschler and Combs are taking over the investment decision-making process."