ON THE BUS there's laughter and gossip, clever-kid quotes and mildly racy jokes. The Sears, Roebuck and W. Bell catalogs and other light reading are hardly cracked because there's a good time to be had trading wisecracks, passing coffee and doughnuts and pulling a number out of a hat for the $10 trip prize.

On the bus they'll tell you this is a ride sanctioned by practicality and thrift -- this day trip to the "outlet capital of the world," Reading, Pennsylvania.

What few will say, though, is that it's also a lark, an adult version of Santa Claus and Easter-egg hunts; a never-outgrown search for the bonuses in life.

So people who wouldn't dream of neglecting children and chores for a purely pleasurable Saturday excursion will get up in morning darkness to pursue bargains among the irregulars and factory overruns and stock surpluses on which the little town thrives.

Every Saturday, in ever-larger numbers as the shopping season ripens, hundreds of them gather at departure places around town and board charters hired by churches, government worker sets, social clubs and other cliques. On the bus a couple of Saturdays ago were the members of the Positive Perspective, Spingarn High's class of '66 alumni club. With mothers, grandmothers and anyone else who wanted to pay $17.50 for the ride, they made their sleepy-eyed, soap-scented 7 a.m. getaway.

The three-hour trip through scenes of stripped fields, white farmhouses and silos was quickened by chattering camaraderie and anticipation. It ended at a dulling redbrick hulk that once hummed with nylon hosiery production and now roared with an ocean of bodies poured out by buses from all over the East Coast and places farther away.

"Hello, shoppers, and welcome to the famous Vanity Fair Outlet Complex, where everything is half-price," an overly cheery loudspeaker voice hailed an audience too busy plundering the wall-to-wall racks of unmentionables to pay any attention.

"Check your courtesy at the door," it might have added, "there's barely jostling room and no place for civility here. In fact, the only way to get near the super buys is to catch a wave in this flood of spenders and ride it to the nearest rack."

"Briefs, girdles, bikinis, pajamas," suggest red-and-white signs as plain and unadorned as the rest of the no-frills atmosphere that make the discounts possible. As in most of the outlets, VF has no sales personnel to help with sizes, no fancy decor or designer shopping bags. Shipping and packing costs are minimal compared to retail establishments.

Most of the 15 or so major outlets do not advertise, but the buses keep rolling in -- 300 or more of them on a busy Saturday in the back-to-school or Christmas shopping season. They come from New York and Tampa, and even Burlington, North Carolina -- itself an outlet town of growing reputation -- snarling traffic in the narrow streets and occupying an entire section of the police force.

"It's phenomenal," says Reading Chamber of Commerce president Anthony Grimm. "Staggering," says Vanity Fair board chairman Roger Gerst.

Reading was a fading knitting-mill center a dozen years ago, many of its factories moving south, when the first outlet opened. Today, though most shoppers don't overnight, Gerst estimates $50 million a year in outlet sales with a multiplier effect of three or four times that in motel, gas-station and restaurant business within the city itself. And that's not to mention spillover to the rest of Berks County, with its sightseeing attraction of the Amish villages, bounteous Dutch Country eating and the antiquing opportunities.

One of the boom stories is that of Reading China, which carries more than 300 patterns of dinnerware and extensive lines of crystal and glass, some of it discounted up to 80 percent. A year and a half old, it threw a big champagne brunch for the trade press last month to celebrate doubling its floor space.

And the pioneer, Vanity Fair, is flagship outlet for one of the most popular shopping clusters. Here's a $42 man's robe in several shades of plush velour for $21, over there $36 negligees in styles from prim to daring for $18, half-price on the $3.50 Dior pantyhose.

"I'm going to be very upset if they don't have some D-cups out," an overladen Philadelphia school principal groans as she's flushed back into the throng.

Bits of loony exchange float out of the din:

"Where's Sandy?"

"She went to look for you."

"She found me but I lost her again."

Line up for the fitting rooms because there's no bringing them back for exchanges. Remove the hangers yourself and have your money ready so the check-out line that stretches the length of the vast fluorescent-lit floor can keep moving.

Move on to the Misty Harbor outlet where signs say everything is "first quality," and 25 to 50 percent less than the retail price. A Kyotie-pile-lined British tan storm coat sells for $99.75.

In the VF shoe outlet, Spanish-made Joyce all-leather shoes, tagged $43, go for $25.98. At Lee Jeans, find a Lee Storm Rider $37 down-lined man's vest for $18, and similar markdowns at Kay Windsor dresses. Pay $18.50 for a $30 silver-plated fruit bowl in the Oneida shop and up to a fourth less on stainless-steel flatware and silver service.

Less of a bargain but quite convenient, the Dutch Treat cafeteria in the basement dishes up whole-meal platters of fried chicken for $3.75, roast beef or ham for $3.25, and sandwiches from a 70 cent hot dog to $1.45 ham and cheese -- all mediocre convenience except the sinfully tempting strawberry pie bathed in whipped cream at 85 cents a slug. Reading veterans say don't waste good shopping time in the cafeteria line: They bring their own and wash it down with fresh-pressed apple cider sold in the parking lot (15 cents a cup, $1.90 a gallon).

Back on the bus there's the momentary wait for the inevitable shame-faced straggler.Across the Schuylkill, the business section in this town of flat-front and gable-roofed row-houses set against late autumn-browned hills is dominated by more outlets.

The block-square Reading Outlet Center, a 1920s textile mill between Moss and North Ninth, is teeming with sale-seekers. Constant bottlenecks tie up narrow stairways and halls between shops offering sportswear and leather goods, men's shoes, yarns and crafts. At the Manufacturer's Outlet, Oshkosh B'Gosh, overall makers for a century, sell them from the littlest -- a $17 size one, for $10.95 -- to the largest, the $28 size 50, for $21.95. (Sizes 50 to 60 slightly more by special order.)

A pair of $54 Stetson tailored boots at the Men's Shoe Outlet costs $27; the $50 Bostonian dress slip-ons for $30. Judy's Closet has up-to-date national brands of women's styles and a whole selection exclusively for big women. Sure as shouting there must be a flaw somewhere in that tweed suit (minus its label) of "pure virgin wool," down from $185 to $95, but none can be found.

Talbott Mills advertises two for the price of one on the lower-quality sportswear sold over bare wood floors, while the carpeted Better Women's Fashions place next to it offers $100 blazers with a handwritten "suggested retail price" tag of $185.

Sore-footed and bone-tired, with ignored hunger pangs, half-block lavatory lines and the all-day press of strange bodies behind them, the Positive Perspective and company face the interminable Interstate homeward with the constructive outlook apparently intact.

Was it worth it?

"Definitely," says a first-timer. "I didn't buy much of anything, but I had a good time looking, and next time I'll know where the bargains are."

A standard 47-passenger coach to Reading costs $522.05 from Gold Line Charters; $493.64 from Triangle Tours. While Reading remains the most popular outlet outing, other increasingly attractive, shopping spots include:

Burlington, North Carolina, an 11-hour round trip from Washington, at $1,014.75 for the bus hire, makes a one-day visit impractical. Bus companies offer package tours including hotel, mainly at the Burlington Holiday Inn, which runs an information center and provides guides among the outlets. This is home of the hosiery mills of the same name, but it also has major outlets for fabric, clothing, handbag and shoe manufacturers.

Burlington, New Jersy, is not an outlet town, but attracts out-of-town shoppers because the huge Moorestown and Cherry Hill shopping malls offer easy access to large inventories among retailers including Gimbel's, Wanamakers, Strawbridge Clothiers and others. The Triangle Tours rate is $562.92 and Gold Line's $590.95.

Closer to home, the newly opened Outlet Mall at 10700 Lee Highway in Fairfax has clothing, luggage, shoes, linens and other discounted merchandise in half a dozen stores and more to come.

Londontown Outlets in Hancock, Maryland, carries irregulars in one brand of "nationally advertised rainwear and outerwear," for adults and children. It's just off I-70 West, about 25 miles west of Hagerstown.