LESS THAN two months till Christmas and we've barely had a chance to savor fall in the country -- of course, there's barely been a fall. Before you head for the nearest hermetically sealed shopping mall to get cracking on your Christmas list, here's a chance to combine a belated autumn outing with a little Christmas shopping at an antebellum mansion in the heart of Virginia's hunt country.

This weekend, Oatlands Plantation near Leesburg launches its annual "Christmas at Oatlands" celebration and, an extra bonus for sporting folk, plays host on Sunday to the Loudoun Hunter Trials. The Victorian Christmas fete, which opens on Friday and continues through December 2, promises candlelight tours of the mansion, decorated as it was in the late 1880s, and an Arts and Crafts Show in the Carriage House, with more than 75 craftspeople and artists from Virginia, Maryland and Pennsylvania.

While the shoppers are busy indoors, outdoor types can enjoy the annual Loudoun Hunt Trials, which get underway Sunday at 10:30. The less-experienced horses and riders jump in the morning, the advanced and team classes in the afternoon. If you prefer dogs to ponies and horses, you may get a kick out of the Jack Russell terrier races, which start at noon. The wiry little dogs leap out of starting boxes and chase after a waving fox's tail. After 200 feet or so of scampering over hurdles, the dogs usually end up in a scuffling pile at the finish line with owners rushing to sort them out.

Even without these special events, the Oatlands estate is reason enough to visit any time of year. The Classical Revival house, built around 1800, was once the center of a 3,400-acre plantation. Boxwood, magnolias and a gazebo grace the terraced formal gardens originally planned by George Carter, builder of the house and great grandson of Robert "King" Carter of Carter's Grove, near Williamsburg.

As well as the house, George Carter built a grist mill, around 1816, and a sawmill on the north bank of the creek. He ground flour for President Monroe's nearby Oak Hill estate and for other thriving farms nearby, and "Oatland Mills" soon became the center of a small community that included a blacksmith shop and a store.

The magnificent southern portico with tall majestic columns and Corinthian capitals wasn't added to the mansion until 1827. Inside, the layout of the house is simple with a wealth of Greek Revival decorative detail and 13 rooms full of finely crafted French and American antiques and art. Two of the house's distinctive features are the large octagonal drawing room and the flights of stairs at either end of the home, instead of the traditional central staircase. In the 1830s, cornices and moldings were added in the drawing room and library and an elaborate ceiling medallion was placed in he entrance hall.

The formal garden, which Carter designed and planted, is one of the finest examples of early Virginia landscape design. Particularly notable are its magnificent boxwoods (both "Tree Box" and English or dwarf box). When Carter died in 1846, he was buried in a tomb at the foot of the garden.

The Carters left Oatlands during the Civil War and Confederate troops moved in. After the War, the fortunes of the family declined steadily and furnishings, family portraits and some of the land had to be sold. Eventually the family had to take in summer boarders. One visitor and family friend, Phoebe Hearst, the mother of William Randolph Hearst, bought the family's portrait of Robert Carter. But the original was copied by one of Carter's nieces before it was shipped to San Simeon and the copy is on view at Oatlands.

In 1903, Mr. and Mrs. William Corcoran Eustis of Washington bought the house, which had fallen into disrepair, and started the task of restoring it and the overgrown gardens. As the Eustis summer estate, Oatlands thrived, becoming a racing and hunting center. The Eustis daughters gave the property to the National Trust for Historic Preservation in 1965. The mansion and its 261 acres of rolling farmland are also protected by scenic easements, making it a picturesque setting for equestrian and historical events.

Although long abandoned by the Carters, every Christmas the plantation bears their personal stamp. A diary written by George Carter's granddaughter serves as the guide for the Christmas decorations. They're strictly authentic and homemade with greens, nuts, pine cones, paper chains, popcorn and fruits that would have been grown on the plantation. COUNTRY PLEASURES

CHRISTMAS AT OATLANDS -- November 9 to 30, December 1 and 2, closed Thanksgiving Day. A Victorian country Christmas is recreated with decorations all grown or handcrafted on the plantation. A special Christmas Shop in the estate's Carriage House is stocked with Christmas crafts and gifts made by more than 75 craftspeople and artists. House and shop hours are 10 to 5, Monday to Saturday and 1 to 5 Sunday. Special candlelight tours of the house are given on Saturday evenings, 6 to 9. Daytime tour admission with refreshments is $4 adults, $3 seniors and children seven to 18; the candlelight tour with refreshments is $5 per person. 703/777-3174.

LOUDOUN HUNTER TRIALS -- Sunday, beginning at 10:30. Ponies and horses compete for jumping prizes, along with Jack Russell Terrier races (at noon). Bring a lunch or buy food at the meet. Admission $5 per car. (Owners of loose dogs immediately fined $5.) 703/777-1550.

GETTING THERE -- Oatlands is six miles south of Leesburg on U.S. 15. From Washington, take Route 7 west and turn south on Route 15 just before Leesburg or take I-66 to U.S. 50 west and turn north from Gilbert's Corner onto Route 15.