GASTONIA - Ask just about any customer standing in line at R.O.'s Bar-B-Cue restaurant why they like the famous slaw sold there, and the answer is the same: "I grew up eating it."

Now, the 56-year-old Gaston County tradition is going national. The slaw is selling to people as far away as California on the family-owned restaurant's new Web site, and hitting shelves in more than 50 area stores -- and counting.

R.O.'s slaw is a gloppy, reddish concoction of cabbage, ketchup, pickle relish and spices that owners still refuse to name. Not even remotely like traditional coleslaw, it's advertised as more of a dipping sauce. Customers line up at the restaurant on Gaston Avenue to eat it mixed with pork barbecue, on burgers or hot dogs, dipped with potato chips or just plain on a bun in a 95-cent creation known as a "slaw burger."

In the last 2 1/2 weeks, the restaurant owners have signed deals with retailers including Harris Teeter and Gaston-based convenience stores Handy Pantry and Kingsway to sell half-pints, pints and quarts of the slaw in stores.

The new retail reach comes from the entrepreneurial drive of the family's younger generation. Their ultimate goal is to sell the slaw in stores coast to coast. But like all products launched by small businesses, the slaw faces stiff competition for shelf space in big stores beyond their backyard.

"We believe in it," said Ruth Black Hoffman, 82, whose mother invented the slaw in the 1940s. Hoffman and her brother Loyde Black, 78, now co-own the restaurant, named for their father Robert Osy Black. "We knew it would sell."

And sell it has, flying off the shelves at the Harris Teeter on Neal Hawkins Road at the rate of six cases a day since it debuted there last Thursday. (Normally, deli salads sell there at a rate of three cases a week, store managers say).

Initial sales at two Harris Teeters were so successful, the Matthews-based chain added two more this week.

Mark Hoffman, Ruth Black Hoffman's son, knew that his mother and uncle wanted for years to sell the slaw in stores, but they didn't have Internet know-how or savvy about approaching retailers.

Hoffman, 48, had tired of his job as a real estate broker and offered to step in with his sister, Manda Hoffman Howe, to form a distribution company. Now, his full-time job is seeking new stores to carry the slaw and overseeing the careful chopping, measuring and mixing of 600 to 800 gallons of slaw each week in the family restaurant. (His mother trained him for two years before she'd let him make the sauce on his own.)

Plans are in the works to build a new facility for slaw manufacturing across the street, he said.

So far, convincing local retailers to carry it hasn't been difficult, he said. Many of those he has approached are already restaurant customers and fans of the slaw, he said.

Harris Teeter hasn't ruled out expanding the slaw beyond the stores in Cherryville, Kings Mountain and two Gastonia locations, said company spokeswoman Jessica Graham, an R.O.'s slaw fan who served it at her own post-wedding party.

"Customer response has been incredible," said J.P. Airhart, co-manager of the Neal Hawkins Road Harris Teeter. "We've been filling the shelves six times a day."

Longtime R.O.'s Bar-B-Cue customers are excited the slaw is becoming more widely available. "It's about time," said Marlene Justice of Gastonia, who's been eating the slaw for about 40 years. "It's going to be sold about a half a mile from my house, so I'll definitely go there to buy it."

Executives at Handy Pantry and Kingsway convenience stores also report the slaw has been popular, selling out in many locations within 24 hours of when it's stocked. (For a list of store locations selling slaw, check www.rosbbq.com or www.bbqslaw.com).

"It was an easy decision (to stock the slaw) because of the local nature of it," said Timothy Roberts, vice president for convenience stores at Handy Pantry.

The Gaston-area retailers agreed it will be more of a challenge to get stores to carry the product when the surrounding population doesn't have the same allegiance to it that Gaston folks do.

"You've got to have more of a marketing effort," said Roberts.

"I certainly believe it will (catch on), once people try it," added Jay King, owner of Kingsway.

To be sure, experts say it's rare for a small, family-based business to crack the shelves of major food retailers. The average grocery store carries between 20,000 and 25,000 products and up to 20,000 new items come on to the market each year.

"The competition (for shelf space) is keener than ever before," said Gene Grabowski, spokesman for Grocery Manufacturers of America.

Harris Teeter's Graham notes that the Matthews-based grocery chain places a high priority on using local suppliers. R.O.'s is the 33rd company based in the Charlotte region to become a Harris Teeter supplier.

Mark Hoffman is confident he can convince more retailers of the magic in his family's slaw.

"It's not a question of if (we expand nationally), but how long it will take," he said.