ON A BRILLIANT late fall weekend, nothing beats driving along winding country roads, looking for treasures in antique shops and stopping in at farmers' markets. And nothing beats the country roads of the Brandywine Valley, where southeast Pennsylvania meets northern Delaware, or the byways of Washington County, a piece of northwest Maryland squeezed in between Pennsylvania and West Virginia.

Both areas are within a few hours of D.C., and along with pastoral countrysides, both offer antique lovers a treasure trove of shops, specializing in everything antique from fine 18th-century English furniture to rare painted colonial pieces, to collectibles like Baltimore hat boxes and turn-of-the-century quilts. And for real antique aficionados, there's Winterthur, the grande dame of American collections, nestled in the Brandywine Valley.

Here's a sampler of the most interesting or unusual shops in both these areas. To be sure the shops will be open, call first, then head for the country and enjoy the hunt.

BRANDYWINE VALLEY

Since the time of William Penn, more than 300 years ago, people have sought refuge in these rolling Delaware hills bisected by the Brandywine River. Today, this lush countryside of fieldstone farmhouses and orchards offers a wide variety of antique stores.

Start your expedition at Winterthur, north of Wilmington, not to buy, but to look. In the 196 rooms of this magnificent country estate of Henry Francis du Pont, you'll find more than 60,000 antiques. From its William and Mary carved wardrobes to 18th-century Pennsylvania blanket chests to its fine examples of Chippendale styling, Winterthur houses one of the most formidable collections of furniture, textiles and other objects made or used in America between 1650 and 1850. It's a place that delights and educates the buyer.

Highlights include the elegant Port Royal parlor, with its balance of matched Chippendale highboys, and lavender and yellow color scheme -- du Pont's favorite; the Chinese parlor, noted for its vivid green Oriental wallpaper, whose four walls panoramically continue the same scene of Chinese village life; and the Montmorenci stairway, a graceful curved staircase rescued from an 1822 home in North Carolina.

Fine furniture merits an equally fine setting: Winterthur, named after the du Pont's ancestral town in Switzerland, sits on 963 elaborately maintained acres full of roses, tall oaks and towering beeches. Walk or take a tram ride through the gardens still brightened by the odd splash of late-fall color.

And with the holiday season fast approaching, this is the time to get a jump on decorating ideas by taking one of Winterthur's Yuletide tours, a 11/2-hour guided tour of 21 specially decorated rooms recreating holiday traditions of early America. (Tours begin Tuesday, and early reservations are recommended; see below for details.)

Within a six-mile radius of Winterthur, along historic routes famous for revolutionary war battles, scores of antique shops tempt the collector with everything from wicker to paintings, from plain used furniture to fine period pieces.

For a small collection of good quality 18th- English furniture and accessories, take Route 52 north to the pink mailbox in Mendenhall, Pa. Be sure to call first, as Margaret Lochtenberg runs the business by appointment from her home. Ashwell Antiques, named after the Hertfordshire village where Lochtenberg honeymooned, offers at least one good example of large pieces such as an 1830 mahogany tilt dining table, a Victorian partner's desk and a painted cottage headboard, bureau and washstand. Lochtenberg also specializes in such whimsical Victoriana as silver stamp boxes, sovereign cases, Prince Albert watch chains, brooches, lockets, lorgnettes and ink wells.

Says Lochtenberg, who trained at the Victoria and Albert Museum, "I buy stuff I like, so if I'm stuck with it, it doesn't matter. I have seven children and they are happy to take anything."

Just up the street (from Ashwell's, continue north on Route 52 about half a mile to Fairville) in a two-room, 200-year-old cobbler's shop, Sally Borton sells formal, but small, 18th- 19th-century American and English pieces, and features silver, needlework, samplers and china.

For primitive American pieces, head north on Route 52 beyond U.S. 1 to a left on Valley Road to Old Goat's Antiques on Echo Valley Farm. Opposite the horse paddocks of this riding school in the hills of West Chester, in a big yellow carriage shed redolent with spices, Judy Murtagh sells a small but interesting collection of children's toys, painted pie safes, jelly cupboards and blanket chests. An 1830 rocking horse swing with the original red paint welcomes you. Atop bureaus and benches there are dolls, a German miniature dollhouse with tiny evergreen trees and a Victorian Noah's Ark, the only toy allowed proper children on the Sabbath since the ark was biblical.

From here, take the scenic backroads southeast to Chadds Ford, on U.S. 1 just west of Pennsylvania Route 100. This is Wyeth country, from the weathered barns to the rolling hillsides. Picnic in the Brandywine Battlefield Park, or dine at historic Chadds Ford Inn, established in 1736 for travelers fording the Brandywine. A favorite for the Wyeths, whose reproductions grace the walls, the restaurant is up the street from the Brandywine River Museum with its impressive collection of Wyeths and other American paintings.

In the Chadds Ford Village Shops next door to the inn, you'll find one of those malls modeled after a colonial pattern. Here, three dealers share Barn Shop Antiques, a store filled with old quilts, antique jewelry, linens, lace, some stained glass and some furniture.

Next, drive north along U.S. 1 (where Washington and Lafayette met General Kynphausen) and then south on Route 352 to a right on Knowlton Road past Linvilla Orchards, one of the largest working farms near Philadelphia. In its octagonal barn you can buy such delights as fresh baked apple and pumpkin pies, sweet corn, tomatoes, ice cream and country preserves.

Fortified, head north on U.S. 1 to Morton (on Route 420, just south of Philadelphia), where you can browse 40 small shops that feature furniture, brass, dolls and china. Brass beds, pedestal sinks and '30s bureaus clutter the sidewalk outside The Lord and Tessler. Harry and Erline Tessler run a general store where prices range from 15 cents to $5,000, and the merchandise ranges from good used furniture to some antiques, to reproduction oak tables.

But save time for Albert Hreha's Carousel Shop. In the gaudy atmosphere of flocked red velvet wallpaper, a row of extraordinary musical machines line the back wall. Part of Hreha's mechanical museum, these turn-of-the-century music boxes for the wealthy -- rendered obsolete by the phonograph -- played musical compositions without electricity by "reading" cylinders, metal discs or paper rolls.

Hreha, who has restored most of these to their original working condition, won't part with most of them. But he will be delighted to play them for you.

There's a Mira Grand 1896 music box that plays tunes from a metal cone; the first juke box, a Regina 1896 player that reads 12 disks; a 1914 reproducing piano that re-enacts an artist's performance by punching patterns in a paper roll; a Mills violano, which plays the piano to violin accompaniment; a Wurlitzer player piano; a 1926 Seeburg 10-piece band that looks like a Rube Goldberg creation with drums, cowbell, xylophone and woodblock; and a bright red crank-up hurdy-gurdy, with everything but the monkey.

After a busy day, take refuge at the many fine restaurants and lodgings. Enjoy American cuisine at Iannucci's Crier in the Country, a handsome restaurant in a charmingly restored Victorian home in Glen Mills, on U.S. 1 between Chadds Ford and Linvilla Orchards; or try Pace One's "American-imaginative" cuisine, in the town of Thornton, (just east of Pennsylvania Route 322). Stay the night at antique-filled bed-and-breakfast homes in the countryside, from large estates to farmhouses, by contacting Bed and Breakfast of Philadelphia.

And for a return to modern times, boogie at Glen Mills' Pulsations, an elaborate disco presided over by Pulsar, the robot, who will undoubtedly fetch a high price from 21st century collectors.

GETTING THERE -- Start your tour at Winterthur, on Route 52 in Delaware. Take I-95 north to Exit 7 in Wilmington and follow Route 52. Or, for a more scenic drive, take I-95 north to Maryland Route 272 north to U.S. 1 north for about 24 miles of rolling countryside to Route 52 south, to Winterthur.

WINTERHUR MUSEUM & GARDENS -- Winterthur, Delaware. General admission $7; reserved tour $10. Open Tuesday to Saturday, 10 to 4; Sunday 12 to 4. Yuletide Tours, November 19 through December 29; Tuesday to Saturday, 10 to 3:30; Sunday, 12 to 5:30. Evening tours beginning December 3, from 6 to 8. Adults $7, children $3.50. For reservations (required) or information, call 302/654-1548.

ASHWELL ANTIQUES -- Chadds Ford, Pa. By appointment. 215/388-2331.

SALLY BORTON ANTIQUES -- Post Office Box 3944, Kennett Pike on Route 52, Mendenhall, Pa. By appointment only. 215/388-7687.

THE OLD GOAT'S ANTIQUES -- Echo Valley Farm, RD 6, Valley Road, West Chester, Pa. 19380. Monday, Wednesday and Friday 9:30 to 3. 215/388-1883.

CHADDS FORD INN -- Routes 1 and 100, Chadds Ford, Pa. 215/388-7361. Open six days a week for lunch and dinner; Sundays 3 to 8.

BRANDYWINE RIVER MUSEUM -- Routes 1 and 100, Chadds Ford, Pa. 215/459-1900. Open daily 9:30 to 4:30.

BARN SHOP ANTIQUES -- Chadds Ford Village, Routeand 100, Chadds Ford, Pa. 215/388-1486. Monday to Saturday 10 to 5; Sunday 12 to 5.

LINVILLA ORCHARDS -- 137 West Knowlton Road, Middletown, PA 19063. 215/876-7116. Open 10 to 6 daily.

THE LORD AND TESSLER -- Morton Avenue and Route 420, Morton, Pa. 215/543-1459. Open Tuesday to Saturday, 11 to 5; Friday till 9.

CAROUSEL SHOP -- Morton Avenue and Route 420, Morton, Pa. 215/544- 1717. Wednesday to Sunday 11 to 6.

THE VILLAGE MALL -- Route 420, Morton, Pa. 215/543-5566. Wednesday to Sunday, 11 to 5. Call first.

FOOD AND LODGINGS

IANNUCCI'S CRIER IN THE COUNTRY -- Glen Mills, Pa. (east of Chadds Ford). 215/358-2411. Lunch and dinner. Also six motel-style rooms $65, and one suite, $125. Includes continental breakfast.

PACE ONE -- Glen Mills and Thornton roads, Thornton, Pa. 215/459-3702. Several bed-and-breakfast rooms, $50 night.

PULSATIONS -- 242 Baltimore Pike (U.S. 1), Glen Mills, PA 19342. 215/358- 5100. Doors open 5:30, show 7:30, nightclub 9:30 to 2:30 a.m.

BED & BREAKFAST OF PHILADELPHIA -- 215/688-1633. Large range of accommodations, many in elegant country homes.

WASHINGTON COUNTY

About 130 miles, as the crow flies, due west of Brandywine and near another battlefield -- this time a Civil War one -- you'll find more excellent antique hunting and fine food in the Sharpsburg area of Maryland's Washington County. This area is best known for Antietam National Battlefield park, site of the bloodiest battle of the Civil War. But there's plenty of history in the antique shops as well. Some of the best shops are just over South Mountain in the nearby towns of Keedysville, Funkstown and Beaver Creek.

In Keedysville, alongside Little Antietam Creek, in an old mill used as a hospital in the Civil War, you'll find two of Maryland's best collections of American country furniture: Fred Hanson's shop occupies the bottom floor and John Newcomer's the gallery above.

Hanson, a gracious gentleman who specializes in fine country furniture and folk art, arranges his shop as a series of charming displays touched with whimsy. Along with signed Windsor chairs circa 1970, farm tables and old quilts, you'll find such surprises as an art deco mirrored dance-floor ball, and a large four-pronged architectural finial. Prices range from under a hundred dollars to several thousand.

Upstairs, Newcomer sells major pieces of Americana and folk art, from a painted Shenandoah blanket chest (circa 1760) priced at $19,000 to a walnut tavern table with original brasses for $2,400.

Before leaving Keedysville, stop by H&H Antiques, north on Main Street. Lower in price as well as quality than Hanson's and Newcomer's shops, but still interesting, the shop stands in the Women's Christian Temperance Hall, built in 1892, where Carrie Nation once came to preach. Here you'll find such country pieces as corner cupboards, pie safes, baby buggies, an old undertaker's cart and cottage headboards and bureaus. Note the small collection of mechanical toys, banks and whatnots in the front display case.

Travel on along Route 34 to Boonsboro, then north on Alternate Route 40 to Funkstown, another country crossroads. On a long block lined with several small antique shops and a real old- time cafe, two dealers stand out: Hudson House, and Ruth's. Diagonally across the street from each other, both offer large collections of good quality 18th-

In a 1770 log house sheathed with wood during the Victorian era, Greg Sullivan of Hudson House conducts old-fashioned antique dealing. "We're here to sell," he asserts. Look carefully in the 10 rooms of furniture and you can find a bargain. Sullivan, a painter as well, specializes in 19th-century paintings by noted American artists.

In Ruth's, the imposing brick house across the street, also a hospital during the Civil War, the sun shines through the rows of colored glass bottles lining the portico. Inside are three rooms of formal furniture and accessories.

For a potpourri of items, try Beaver Creek Antiques, on U.S. 40 just east of I-70, where 50,000 square feet display the offerings of 48 dealers from glassware and china to tables, railroad chests, peg legs, dolls and even a child's coffin. This is a good place to search for small collectibles, as each dealer offers several. The prices and quality vary. Swing as you browse to an array of '30s hits played on two period console radios.

For dinner, you can have an unlimited buffet of fish and chicken at Richardson's Restaurant, about two miles west of Beaver Creek on U.S. 40, in Hagerstown. While the quality varies, the prices and quantity fit the budget of weary families with hungry children.

For fine dining, relax at the Old South Mountain Inn, about one mile east of Boonsboro on Alternate Route 40. The inn was built in 1732, and legend has it that such notables as Abraham Lincoln, Henry Clay and Daniel Webster played checkers here in front of a roaring fire. The Battle of South Mountain preceded Antietam, and the inn was pressed into service as a hospital.

Or, like Lee after the battle of Antietam, retreat to Shepherdstown, West Virginia, a short drive west across the Potomac on Route 34. This charming town, the oldest in West Virginia, is home to The Yellow Brick Bank restaurant at 201 German Street. In a converted turn-of-the-century bank, you can dine on "new American cuisine," enjoying such fine house specialites as raspberry chicken or mesquite-grilled swordfish.

If you're tired out, stay overnight upstairs in one of the two rooms and a suite. The eclectic decorations -- dark green walls and funky overall effect, which appears a bit tired in places -- may not appeal to everyone.

At the other end of German Street, at the corner of Duke, the Thomas Shepherd Inn, a large, cream-colored Federal style home, built in 1868, offers a cozy retreat filled with colonial and country antiques.

For another charming bed and breakfast home, cross the bridge again into Maryland, and drive the short distance along Route 34 to the Inn at Antietam in Sharpsburg. The hosts are gracious, and this turn-of-the-century house, surrounded by the battlefield, is pleasingly furnished with Victorian antiques. The glassed sun room filled with wicker and plants provides a pleasing place to chat with a view of the Blue Ridge mountains. From the wrap-around porch or a spot under the huge silver maple that stood guard during the battle, you can enjoy this pastoral but once violent countryside.

ANTIETAM NATIONAL BATTLEFIELD & CEMETERY -- P.O. Box 158, Sharpsburg, MD 21782-0158; 301/432-5124. Visitor Center is on Maryland Route 65, near Route 34. To get there, take I-270 north to to I-70 to Alternate Route 40 to Boonsboro, left on Route 34. Open September to May from 8:30 to 5; June to August, 8 to 6. Park closes at dark. No fee.

FREDERICK B. HANSON COUNTRY ANTIQUES -- Pry Mill, Box 35, RD 1, Keedysville, MD 21756; go 3.3 miles west of Boonsboro on Route 34, turn right on Keedysville Road for half a mile; shop is on the left in a two-story grist mill. 301/797-3895. Saturday and Sunday 11 to 6, or by appointment.

JOHN C. NEWCOMER AMERICANA -- Pry Mill, Box 35A, RD 1, Keedysville, MD 21756. 301/790-1327. Saturday & Sunday 11 to 6, or by appointment. Same directions as Hanson's.

H&H AMERICAN ANTIQUES -- Keedysville, Md.; drive north up Keedysville's Main street for about a mile. Mailing address: Rte. 1, Box 308, Rohrersville, MD 21779. 301/432-8012. "Nine to five when we're here. Call first."

HUDSON HOUSE GALLERIES -- 32 East Baltimore St., Funkstown, MD 21734. 301/733-1632. 10 to 5 all week.

RUTH'S ANTIQUE SHOP -- U.S. 40A, Funkstown. 301/739-0311. 10 to 4 daily; closed Sunday and Tuesday.

BEAVER CREEK ANTIQUES -- U.S. 40 east of I-70. 301/739-8075. Open 9 to 5 daily except on Wednesdays. From the Funkstown shops, take Hebb Road east to a right turn on U.S. 40, for about a mile.

FOOD AND LODGINGS

RICHARDSON'S RESTAURANT -- 710 Dual Highway (U.S. 40 east), Hagerstown, Md. 301/733-3660. Open Sunday to Thursday 7 a.m. to 10 p.m., Friday and Saturday till 11 p.m. From Beaver Creek Antiques, go west on U.S. 40 about two miles.

OLD SOUTH MOUNTAIN INN -- Route 3, Box 459, Boonsboro, MD 21713. 301/432-6155; 371-5400. Dinner Tuesday to Sunday, Saturday lunch 11:30 to 4; Sunday brunch 10:30 to 2. Closed Monday.

YELLOW BRICK BANK RESTAURANT -- 201 German Street, Shepherdstown, West Virginia. 304/876-2208. Lunch Friday to Monday, 11:30 to 3; dinner daily. Bed and breakfast: two rooms and one suite. Private bath. $75 per room. includes full breakfast served in room.

THOMAS SHEPHERD INN -- Duke and German streets, Post Office Box 1162, Shepherdstown, W VA 25443. 304/876-3715. Six guest rooms, four with private bath. Shared bath $52.50; private bath $55. Includes full breakfast.

INN AT ANTIETAM -- Betty and Cal Fairbourn, hosts. 220 East Main Street, Post Office Box 119, Sharpsburg, MD 21782. 301/432-6601. One suite with private bath, $65; two rooms with shared bath, $40; and two with private bath, $45. Includes ample continental breakfast.