AN EXCURSION down Route 301 will nourish and enrich mind and soul, but you can't indulge in "l'affaire gastronomique" -- this is basic pig-out country.

If you hop onto Route 301 from its junction with U.S. 50, don't bypass Rip's Country Inn. Worry not about timing, they're open early with such eye-openers as a homestyle Hunt Breakfast or egg on muffin with filet mignon and asparagus. If you stop by on your way home, you'll do as well with their homestyle dinner entrees. While you wait for your rum-sauce bread pudding, ponder what prompted the sign declaring "These booths are for dining only."

Consider sampling a couple of regional specialties down the road a piece -- picture-perfect Southern Maryland stuffed ham or Popes Creek crabs.

According to Cassandra Deck of Alexandria, whose family hails from St. Marys County, tradition has it stuffed ham was invented by a slave cook at St. Inigo Manor House in southern Maryland in the early 1700s. She used what was available: a country-cured ham, fresh greens from the gardens, and a pungent mix of spices and hot red pepper, which had been ground with a mortar and pestle. If it's on the menu, order it.

On the crustacean front, the tiny community of Popes Creek is noted for its crab houses stacked on piles over the Potomac River. Extra windows and broad views come free with the mountains of spice-laden crabs. Popes Creek Pier and Robertson's Crab House are just two of the places that will leave you with a smug smile and burned lips.

The following list of restaurants, grouped by area, were recommended by locals and other experts. For a complete list of dining possibilities, check with the Charles County Chamber of Commerce, P.O. Box 1628, 870-3089, or the Fredericksburg Area Chamber of Commerce, 703/373-9400. BOWIE/MITCHELLVILLE

RIP'S COUNTRY INN -- Award-winning country ambience and meals that taste home-cooked. Dinner entrees range from $7 to $16. Open 8 a.m. to 10 p.m. weekdays and Sunday; 8 to midnight Friday and Saturday. Route 301, 3809 N. Crain Highway, Mitchellville, MD 20716. 301/262-2963. WALDORF/LA PLATA REGION

ARCHIE'S -- Another place where everything tastes homemade. On left side of Route 301, in the middle of Waldorf across from Martha Washington Motel. Open daily 7 a.m. to 10 p.m.; to 11 p.m. on Friday and Saturday. 301/645-1361.

MARIE'S FAMILY RESTAURANT -- The folks at the Charles County Chamber of Commerce swear by the fried chicken and stuffed ham. Very reasonable prices; try the soups. Open 7 days a week, 7 a.m. to 9 p.m. (Fridays until 10). Route 301 in La Plata, next to a 7-Eleven Store. 301/932-6884.

MARYLAND WAY RESTAURANT -- Just about any Maryland food or beverage you can imagine. Route 301 and St. Patrick's Drive in the Waldorf Holiday Inn. Open 6:30 a.m. to 2:30 and from 5 to 10 p.m. daily; open Sunday 6:30 a.m. to 10 p.m. 301/645-8200.

PENNY'S BARBECUE -- Chicken, ribs, chops. From Route 301 in Waldorf, turn left (south) on Rte. 925 (Old Washington Road) for one mile. Open noon to 9 p.m. No phone. Expect a line.

PHILADELPHIA HOUSE -- This sub and sandwich shop whips up authentic Philly-style fare. Is that (gasp!) provolone instead of Cheez-Whiz on the cheese-steak? "This is Waldorf," mutters the waitress. As you travel south from D.C., on the right side of 301, in Waldorf across from Dunkin' Donuts. Open 11 to 9; 11 to 10 Friday and Saturday; Sunday noon to 5. Closes on Sundays for the summer beginning in late June 301/843-7530.

SMOKEY JOE'S BAR-B-QUE -- Pretty decent, which would describe just about all the barbecues around here. Route 4 and Route 301, near Summer only (after Memorial Day); call for hours. Waldorf. 301/645-1287. POPES CREEK AREA

POPES CREEK PIER -- Crabs, crabs and more crabs. Oh, and fresh seafood in season. About 2 miles north of Potomac River Bridge; from 301, turn right on Popes Creek Road three miles to crab house. Open 11 to 9 daily (hours depend on number of customers). 301/259-2114.

ROBERTSON'S CRAB HOUSE -- Look for a table by a window overlooking the docks. Open April-October, Route 301 about 6 miles south of La Plata, right on Popes Creek Road at restaurant sign. Until May 26, Friday and Saturday 11 to 11; Sunday 11 to 9; after May 26, 11 to 11 daily. 301/934-9236.

MR. CRAB'S SOMBRERO -- A happy, if strange, marriage of "A little bit of Mexico, a whole lot of Maryland." On the waterfront, south of La Plata at Aqualand by the bridge. Open 11 to 10 daily. 301/259-4477. VIRGINIA SIDE OF BRIDGE

A.J.'S NORTH CAROLINA BAR-B-QUE -- More good excuses to lick your fingers. Indoor seating. On Route 301 in Dahlgren. Summers only, call for hours. 703/663-3770.

CADDEN MANOR RESTAURANT -- Real southern-style food and personality, where you can get the likes of one-quarter of a fried or smothered chicken for $1.85. The world's friendliest people live in Port Royal. Turn left into town from Route 301, go 2 blocks to Cadden Manor. Open 11 to 10 weekends only until warm weather. Summer hours 11 to 10 daily. 804/742-5579.

EARL AGEE'S BAR-B-QUE -- Fantastic food; more of those nice Port Royal people who always call you "honey." Open 11 to 8 daily; closed Wednesday and Sunday. In Port Royal on left side of Route 301, just south of the James Madison Bridge over the Rappahannock River. 804/742-5769.