NEW YORK (

TheStreet

) -- Tom Ognar, portfolio manager of

Wells Fargo Advantage Growth Fund

(SGROX)

, is part of a noteworthy father-son act. Tom's father, Ron Ognar, started the fund in 1993. When the father retired, the son took over the reins in 2003. Both Ognars have delivered outstanding results. During the past five years, the Wells Fargo fund has returned 8.4% annually, outdoing 99% of large-growth competitors. Over the past 15 years, the Ognars have returned 8.5% annually, outdoing 91% of peers.

Much of the credit must go to the senior Ognar who developed a flexible approach while managing money for a bank in the early 1970s. Like many investors at the time, Ognar loaded up on a group of big blue chips that were then known as the Nifty Fifty. The list of sought-after names included

American Express

(AXP) - Get Report

,

Baxter

(BAX) - Get Report

and

Texas Instruments

(TXN) - Get Report

. Convinced that the star stocks would grow reliably for years, investors bid the price-to-earnings ratios up to more than 50.

By the mid-1970s, inflation and rising interest rates clobbered the Nifty Fifty, and Ognar suffered along with the crowd. But the episode taught him the hazards of paying high prices and focusing on a narrow group of market leaders.

In 1993, Ognar joined Strong Capital Management and was assigned the task of building a growth fund. While most of his competitors focused on niches, such as large-caps, he developed a flexible portfolio that could hold stocks of all sizes. Ognar studiously avoided stocks like the Nifty Fifty that came with sky-high prices.

After being caught up in an industry trading scandal, Strong Capital collapsed and sold its funds to Wells Fargo in 2004. Throughout the turmoil, the Ognars continued employing their disciplined approach.

Today, the younger Ognar still follows his father's strategy, looking for the best growth stocks of all sizes. He seeks companies that can deliver at least 5% annual revenue growth for sustained periods of time.

"We are not interested in a company that will have one great year and then seven bad ones," he says.

Most companies do not qualify for the portfolio because they are not growing fast enough, says Ognar. For example, he cannot buy

Home Depot

(HD) - Get Report

or

Wal-Mart

(WMT) - Get Report

, which are only opening a few new stores each year. Instead, he owns

Tractor Supply

(TSCO) - Get Report

, a retail chain with 930 outlets that is increasing its store count by more than 5% annually. The retailer sells products aimed at rural homeowners, including riding lawn mowers, fencing, and outdoor apparel. Sales per store are growing as the company introduces new merchandise and brings in more customers.

Like his father, Tom Ognar steers away from stocks with steep prices. To spot bargains, Ognar looks for companies with price-earnings multiples that are lower than their historical levels. One of his top holdings is

Apple

(AAPL) - Get Report

. In the last quarter, revenue increased by 66%, but the shares only sell for 16 times next year's estimated earnings. That is a modest figure for a technology star, says Ognar. When companies such as

Microsoft

(MSFT) - Get Report

and

Cisco Systems

(CSCO) - Get Report

were market darlings in the past, they often sold for multiples of 20 to 30.

Ognar has a big weighting in health stocks because valuations have slumped as investors worry about the outlook for product pipelines. A favorite holding is

Abbott

(ABT) - Get Report

. Revenue has been growing at an 11% annual rate, but the shares only sell for a forward P/E multiple of 11. Another holding is

St. Jude Medical

(STJ)

, a maker of cardiovascular devices. Revenue has been growing at a 7% rate, and the shares sell for a forward P/E multiple of 12.

The willingness to hold stocks of all sizes has helped the Ognars excel. Earlier in the decade, the fund had most of its assets in small- and mid-cap stocks. That proved to be a winning move because large stocks lagged. These days, the fund is heavy on large-caps.

"Compared to where they traded in the past, large-caps are about 20% undervalued," says Ognar. "Small- and mid-cap stocks are trading for average valuations."

No matter which size stocks they have emphasized, the Ognars have delivered consistent results. In nine of the past 10 years, the fund has finished in the top half of its category.

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Stan Luxenberg is a freelance writer specializing in mutual funds and investing. He was executive editor of Individual Investor magazine.