We generally don't know what stocks Warren Buffett and the rest of Berkshire Hathaway's (NYSE:BRK-A) (NYSE:BRK-B) stock-picking team are buying until the company's 13-F is released. However, Buffett confirmed in a recent interview that he has bought two stocks in particular since the second quarter ended.

Specifically, Berkshire's Apple (NASDAQ:AAPL) stake has gotten even larger, and the company has started buying back its own stock for the first time in years. Here's a rundown of what we know, why Buffett could be making these moves, and whether investors should follow Buffett's lead and invest in these two companies.

Warren Buffett in a grey suit.

Image Source: Getty Images.

Even more Apple

Tech giant and iPhone maker Apple is already the largest stock position in Berkshire Hathaway's portfolio by a wide margin. As of the end of the second quarter, Berkshire owned nearly 252 million shares of Apple, which translates to more than 5% of the trillion-dollar company and is worth about $56.7 billion at the current share price.

However, it appears that Buffett isn't done accumulating Apple stock just yet. In a recent CNBC interview, the Oracle of Omaha said that he has added "just a little" to the Apple stake since the end of the second quarter.

There are a few reasons why Buffett loves Apple as a business. Perhaps most significantly, Apple has a massive and fiercely loyal customer base. Buffett noted in the interview that Apple's customers find its products "indispensable" and that even though $1,000 may seem like a lot for a smartphone, "the iPhone is enormously underpriced," considering how useful it is.

Buffett pointed out that he's not concerned with how many iPhones are sold in a given quarter, or even in a given year. Instead, Buffett is taking the long-term view, saying, "I focus on the hundreds, hundreds, hundreds of millions of people who practically live their lives by it."

This move by Berkshire helps answer the question: "Is Apple still a good buy?" The stock has risen by about 22% since the end of the second quarter and is at an all-time high, so it may seem like it's getting a bit expensive.

AAPL Chart

AAPL data by YCharts.

Keep in mind, however, that Buffett will only invest if he thinks a stock is a good value relative to the intrinsic value of the business. So, by adding even a little to Berkshire's Apple stake, Buffett is indicating that he still thinks Apple has more upside potential ahead of it.

The first Berkshire buyback in years

In the same CNBC interview, Buffett confirmed that he has taken advantage of the company's looser buyback authorization and that the company had already bought back some of its own stock.

In an effort to combat its massive (and growing) stockpile of cash, Berkshire's board significantly modified the circumstances under which Buffett and his team are allowed to use Berkshire's capital to buy back stock.

Previously, Buffett was only authorized to buy back shares when they were trading for less than 1.2 times book value, a level shares hadn't dipped to in several years. Now, shares can be repurchased at any time Buffett and Vice Chairman Charlie Munger agree that the stock price is below its intrinsic value.

Buybacks cannot reduce Berkshire's cash hoard to less than $20 billion, but with $111 billion in cash and equivalents at the end of the second quarter, this isn't really much of a restriction. The new buyback plan required Buffett to wait until after its second-quarter earnings report, which was released just a few weeks ago. So, it appears Buffett was eager to get started.

The point is that even though Berkshire's stock has risen by about 20% over the past year, Buffett (and Munger) must think that it's still a compelling value. After all, Buffett has said that he uses "conservative" methods to compute Berkshire's intrinsic value, so it's fair to assume that Buffett thinks Berkshire is really worth significantly more than the roughly $210 each of its Class B shares are currently trading for.

Should you do the same?

To be perfectly clear, I don't suggest buying a certain stock just because a billionaire is doing it -- even if that billionaire is Warren Buffett. Having said that, when Buffett indicates that a stock is worth significantly more than its current price, I tend to listen. It's always a good idea to do your own research, but Apple and Berkshire Hathaway could be two stocks to consider in a historically expensive stock market.

Matthew Frankel, CFP owns shares of Apple and Berkshire Hathaway (B shares). The Motley Fool owns shares of and recommends Apple. The Motley Fool has the following options: long January 2020 $150 calls on Apple and short January 2020 $155 calls on Apple. The Motley Fool recommends Berkshire Hathaway (B shares). The Motley Fool has a disclosure policy.