THE moral and physical welfare of mankind depends largely upon its breakfast," warned Mrs. Beeton, whose classic, The Book of Household Management, is an examplar of domestic wisdom. In Washington, where breakfast might be the setting for a summit conference or a task force meeting, Mrs. Beeton may be more right than she knew.

People have been eating breakfast ever since there have been people. But they have not been eating it by that name since the fifteenth century, and have only been eating what we call breakfast in the last hundred years. When the day's first meal was first known as breakfast, the English version consisted of boiled buttock of beef and ale (stale, at that). Bread was sometimes included, and salt or pickled fish. Later it grew to include eggs, bacon, porridges, jams, even woodcocks and snipes. Now it consists of, among other things, more than $1.5 billion worth of processed cereals.

If any meal in America is rigidified and circumscribed, it is breakfast. Not only are orange juice, eggs or pancakes or French toast with ham, bacon or sausage, cereal, toast and coffee the requirement for many an eater, they are the outside limits of what many will consider even lookin at early in the monring. Thus, there would not seem on the surface to be much that distinguishes one American restaurant breakfast from another.

Not so. Orange juice can be fresh or frozen - occasionally even canned.Eggs, simple as in their preparation, are material for all manner of culinary offenses. Breakfast meats, besides being stingy or generous, can be greasy bland sludge or woodsmoked succulence. The coffee - ah, the coffee - we all know how abominable or stirring can be a cup of coffee.

So here are three restaurants that presume to make a big fuss over breakfast. Two of them are worth the fuss.