Long-term Investing

Apple: Most widely held stock in 401(k) portfolios

Apple: Most widely held stock in 401(k) portfolios
Apple: Most widely held stock in 401(k) portfolios

Many investors may not realize it, but your 401(k) plan probably includes a lot of tech stocks—some even volatile tech stocks. Do you know what stocks are in the mutual funds in your 401(k)?

It's pretty easy to find out the top funds in your 401(k), but it takes a little more digging to find out the most widely held stocks in those funds. Who has the time to do that much homework? Well, we did it for you—and you may be surprised to learn what we discovered.

We asked Brightscope, a website that rates plans of more than 45,000 employers using hundreds of data points obtained from publicly available data, to tell us which mutual funds dominate the 401(k) landscape.

(Read more: Why 401(k) savers don't have enough to retire)

Getty Images

According to the company, the top five U.S. equity mutual funds in most 401(k) plans are , Fidelity Spartan 500 index, American Funds Growth Fund of America, Vanguard Institutional index and Vanguard 500 index.

Next, we asked researchers at Morningstar to compile a list of the most widely held stocks in these funds, based on the total number of mutual funds that hold this security. In addition to the top five 401(k) funds, nearly 1,000 mutual funds—or more—own these stocks. Here is the list three tech companies you may not have realized you likely own in your 401(k).

Microsoft. The company has been very popular in the past few year among those looking for value, experts say. With shares up more than 35 percent so far this year, that strategy has certainly paid off in 2013. Microsoft is also favored for its regular stream of dividend payments, a strong draw among investors and fund managers alike.

(Read more: Active managers rebound)

Google. The search engine ranks high in terms of usage. And while it's clear that lots of users love Google, so do investors. Google ranks as the second most-owned holding in 401(k) plans. Shares have rallied nearly 45 percent year-to-date.

(Read more: The best retirement investment you can't have)

Apple. Chances are, you not only own an Apple iPhone, iPad or iMac, but you also own Apple shares. With its stock hitting a high of $700 per share in September 2012, investors who piled into it last fall may have wished they'd taken a smaller bite. Apple's market value has fallen about 25 percent since then, with the stock trading around $525 a share.

But even with the slide, Apple's stock price has soared—gaining more than 400 percent in the past five years. So it should come as no surprise that some of the top equity funds in 401(k) plans have allocated 3 percent to 4 percent of their holdings into that single name.

—By CNBC's Sharon Epperson. Follow her on twitter: @sharon_epperson.