QUESTION: I would like to spend some time on a working farm in the Midwest before and during the harvest. Can you help? ANSWER: A number of working farms throughout the country take paying guests, many of them offering the opportunity to participate in or just observe the day-to-day business of the farm.

Some provide such diversions as horse riding, fishing and swimming; others offer simply accommodations and the chance to be part of a rural family, if only for a day or two.Three farms that might suit your purposes are in Ohio, Iowa and Indiana.

The Circle K Ranch, in Circleville, Ohio, has been taking paying guests since 1968. The 200-acre wooded farm has a creek stocked with fish and grows corn, soybeans, oats, wheat and hay.

The hay harvest is in the summer, usually July, wheat and oats from June to August. Soybeans and corn are harvested in the fall, usually in October. Accommodations are in a six-room cottage that is equipped with linen and kitchen utensils.

From June to September rates are $275 a week for up to four people. From the middle of April to the end of May and in October only weekends are available. Rates are $20 a person, with a $60 minimum.

More information: Cliff and Marjorie Kerns, Circle K Ranch, 26525 Gay-Dreisbach Road, Circleville, Ohio 43113; telephone (614) 474-3711.

The Centennial Farm, in Webster City, Iowa, has been in the family since 1869. It is surrounded by fields of corn and soybeans (harvesting is in October and November) and is near golf and canoeing.

The four guest rooms, with shared bath, are available all year for $35 a night for two people, $25 for a single. Full country breakfast is included, and lunch and dinner are available in either Highview, two miles to the east, or Duncan, two miles to the west. Webster City, which has a full range of restaurants, is seven miles to the east. More information: Tom Yungclas, Rural Route 2, Post Office Box 40, Wesbster City, Iowa 50595; (515) 832-3050.

The Bee Hive B&B is in the heart of Amish country in Indiana. Its 360 acres are planted with oats and wheat (harvested in July) and corn and soybeans (September to November).

The owners, Herb and Treva Swarm, have a collection of antique farm machinery, some of which is used in July for threshing. Rates in a guesthouse that adjoins the farm (two double beds) are $63 a night, with a full breakfast. Three rooms in the house rent for $52.45 a night, also with breakfast. More information: Post Office Box 1191, Middlebury, Ind. 46540; (219) 825-5023. A useful guide to farm vacations and overnight stays has been published for 40 years by Farm & Ranch Vacations, 36 East 57th Street, New York, N.Y. 10022; (212) 355-6334 or (800) 252-7899. The book, "Farm, Ranch & Country Vacations," by Pat Dickerman, is available from the publisher for $12, including postage.