Vacations by Seniors Specialist Take in Holidays : Domestic tours include visits to the Southwest at Christmas and New Year’s.

A bountiful offering of late summer and fall trips is being offered by 10-year-old Trieloff Tours, one of the leading packagers of vacations for mature travelers. Owner Jim Trieloff has been working with senior groups since 1974.

Trieloff Tours covers destinations throughout the world, as well as cruises. Most of the tours include most meals, gratuities, local guide service, room accommodations and, except as noted, round-trip air transportation from Southern California. Quoted prices of some upcoming tours below are per person, double occupancy.

* England, Scotland, Wales and Ireland. Tour by motor coach and ferries to see most of the famous cities and landmarks of the United Kingdom, including London, Dublin, Stratford-on-Avon, Stonehenge, Windsor Castle, Edinburgh, Glasgow, Liverpool and Cornwall. Departs Aug. 29; 22 days, $2,625.

* The Colorado Rockies and scenic parks of Wyoming, Colorado, Utah, Idaho and South Dakota. Travelers fly to Denver and continue by coach. Stops include Grand Teton, Yellowstone and Badlands national parks, Mt. Rushmore and Salt Lake City. There is also a ride on the Silverton-Durango narrow-gauge railroad. Departs Sept. 8; 13 days, $1,499.

* A fall foliage tour of New England and Canada. Travelers fly to Boston and continue by motor coach through Massachusetts, Maine and New Hampshire. Canadian stops are in Halifax, Nova Scotia and St. John, New Brunswick, with spectacular scenery along the way. Departs Sept. 28; 10 days, $1,499.

* Mexico’s magnificent Copper Canyon. Travelers fly to Los Mochis on the Sea of Cortez, then board the Chihuahua Pacific Railroad train through the Copper Canyon, with sightseeing and meal stops along the way. Ends in Chihuahua, the state capital and former home of Pancho Villa, for a farewell dinner and folkloric dance show. Departs Oct. 25; eight days, $1,299.

* The Old South and the Great Smoky Mountains. Travelers fly to Atlanta and continue through such historic places as Warm Springs, Ga.; Asheville, N.C.; Great Smoky Mountains National Park; Charleston and Hilton Head Island, S.C., and Savannah, Ga. Departs Nov. 7; nine days, $1,299.

* Australia and New Zealand, including Auckland, Rotorua, Wellington, Greymouth, Queenstown, Christchurch, Melbourne and Sydney. This trip offers a close-up look at the lifestyles of the Kiwis and Aussies. Departs Nov. 12; 22 days, $4,499.

* Christmas in San Antonio featuring the Fiesta de las Luminarias, the candle-lighting ornament tradition of the Southwest. Includes all of the historic and scenic sights of San Antonio, including the famed River Walk and the Alamo, plus Austin, Tex., including the LBJ Ranch. Christmas Eve dinner and a Christmas Day luncheon in Austin are part of the package. Departs Dec. 21; six days, $899.

* Christmas in Tucson, a compact holiday tour in the Arizona desert that includes historic museums, resort hotel accommodations, a gala dinner on Christmas Eve and another one on Christmas Day. Lots of holiday sights and sounds. Departs Dec. 23; five days, $899.

* New Year’s in Arizona, including a stop in Laughlin, Nev., then on to the Arizona cities of Flagstaff, Sedona and Phoenix, where travelers will catch the Fiesta Day Parade and then a gala New Year’s Eve dinner celebration. Departs Dec. 28; six days, $699.

Trieloff Tours also offers a choice of escorted, all-inclusive sightseeing and golf vacations in Hawaii, ranging from 8 to 15 days. For complete itineraries and tour components on all of the above tours, contact your travel agent or Trieloff Tours, P.O. Box 2100, Laguna Hills 92653, (800) 432-7125. From outside California, call (800) 248-6877.