Marion Stoddart, the 62-year-old founder of Outdoor Vacations for Women Over 40, organizes two dozen nature and outdoor adventures each year, according to Changing Times, the Kiplinger magazine.

Ten to 16 participants, most of them in their late 50s and 60s, take trips ranging from one-day and weekend trips in the New England area to six- to 16-day vacations all over the world. Costs run from $45 to $290 for one-day and weekend trips, and longer vacations start at $1,250.One of the most rigorous trips, a $2,395 adventure that includes an optional hike to the bottom of the Grand Canyon, is among the most popular. Some of the vacations planned for 1991 are a walking tour in Yorkshire, in England; Alpine hiking in Switzerland and France; and rafting the Salmon and Snake rivers in Idaho.

For a schedule of upcoming events, write to Outdoor Vacations, P.O. Box 200, Groton, MA 01450, or call 508-448-3331.