MILLERTON, N.Y. — THE nearest decent restaurant (''very good Tuscan food'') is seven miles away from here in Amenia, N.Y. But Tim Zagat is not dismayed. ''Quite frankly, our fundamental goal in life when we are up here is not to eat out,'' says Mr. Zagat, who is sitting in his country farmhouse, two hours north of New York City. Excuse me, did Zagat say he and his wife, Nina, were not interested in dining at a gracious inn whose owner is anxious to fix his place in the gastronomy universe? Yes, this is a man who eats out six to seven times in five days when he is in Manhattan. But when he's in the country, he only wants to inhale ham and turkey open-faced sandwiches with local yellow tomatoes leaking their juices over English muffins. This is also the same man who surprises a visitor by announcing that he can review a restaurant without even going there. Before you can say ratatouille, Zagat has opened up a loose-leaf binder filled with all the statistics that a sportscaster - make that a restaurant reviewer - needs to know. Okay, Tim. ''Ever been to Ottoman Cuisine?'' ''Never.'' Here's the review: ''Good Turkish food with simple decent good service.'' No, Zagat is not playing Johnny Carson's psychic ''Carswell'' trying to answer questions before Ed McMahon asks them. Instead, he's looking at the statistical compilation of 66 reviews of Ottoman sent in by a small portion of the 16,000 New York reviewers who rate restaurants on the basis of food, service, decor, and cost, and also list their own five favorites. Of course, had he gone to the restaurant, Zagat might have mentioned the best stuffed grape leaves this side of the Bosporus, or the manti, a mint and yogurt Turkish lasagna that could end regional conflicts if served to combatants. Over the next several weeks, Zagat will spend a significant portion of his time poring over the volumes of comments and numbers before the New York City restaurant guide hits the bookstores in mid-November. This year, Zagat's publishing company will print 26 books (75,000 surveyors) for 40 US markets. In 1988, Zagat expanded into rating hotels, resorts, airlines, and car-rental agencies. Zagat, who is really like a foodie pollster, has expanded the guides into a computer-software program called, ''Taxi with Zagat's Survey.'' He is now working on a CD-ROM that will include seating charts and photos of the food in each restaurant. As he thumbs through the 1996 statistics for the New York City guide, Zagat mentions some of the survey's winners, which he'll keep under wraps for now. In the case of a restaurant like Bouley, for which 4,000 surveys were returned this year, Zagat estimates each diner has visited the restaurant four times in a year. With at least two people per visit, more than 30,000 meals are represented in the survey for one restaurant. ''This is a substantial portion of the meals eaten there, and it is as close to scientific as you can get,'' he says. After years of tasting meals both good and bad, Tim and Nina have some firm opinions about what diners should expect. Nina on food: ''The most important thing is great ingredients - the better the ingredients and the less that is done to interfere with their basic qualities, the better the restaurant.'' Tim on food: ''The quality of the chef is the next most important thing - as much of that is restraint as preparation.'' Tim on decor: ''A lot of what you are looking for is dictated by your needs and how you feel. I think Bouley is a beautiful restaurant, but I wouldn't go there more than once every four months.'' Nina on service: ''There is a line where if you get too-terrific service, it's an intrusion.'' Tim on service: ''When a waiter comes along and introduces himself ... you don't want him to participate in your lunch or dinner at that level. Fifty percent of the things that irritate diners are service related.'' Tim on price: ''People have expectations - they might be willing to pay $60 per head at a fancy French restaurant in New York.'' If the bill comes in lower than expected, people are happy. Tim on why they keep cranking out the books every year: ''We love food.''