WHEN THE last sip was taken at the New Zealand embassy last Friday, it became clear that the home team had won. Steinlager, the New Zealand brew, was selected best in a three-way tasteoff, an unprecedented finale to the annual Les Amis du Vin beer tasting.

It was Steinlager's fifth consecutive triumph. The challengers, in a field of 28 golden entries, weren't household words such as "Bud" or "Lite." They were expensive, premium beers from faraway places -- Fischer from Alsace in France and Julbrew from Gambia in Africa.

More than 200 persons had participated in the blind tasting organized by the wine society. Beers were entered by distributors, which may explain the absence of Budweiser and Miller, America's two best-selling, most advertised brews. Neither had fared well in the group's previous tastings. Other domestic favorites were on hand, however, among them Erlanger, Nationall Premium, Stroh's, Schlitz, Old Milwaukee, Pabst and Carling Light. In all, breweries in a dozen countries took the soon damp and slippery field.

Total points, computed from about 180 score sheets, led to the three-way tie. The top 10 was completed by -- in order -- Dos Equis, St. Pauli Girl, Grolsch, Beck's, Heineken, Erlanger and Labatt's Ale.

With the cooperation of the New Zealanders, Doug Burdette of Les Amis and the Calvert Wine Shop organized the tasteoff. On the appointed day, three French diplomats joined the New Zealand representatives, leaving Gambia's lone representative, embassy First Secretary Galandou Gorre-Nadiaye, distinctly outnumbered. There were, however, a dozen or so impartial tasters present and the beers were presented in unmarked pitchers.

Beer tasters behave in much the same fashion as wine tasters. They check color, aroma and taste; look for flavor comparisons and balance. They also measure the size and durability of the foamy head and the size of bubbles. aSteinlarger, a well-balanced, fragrant brew with more carbonation than its competitors, drew nine first-place ballots. Jul-Brew and Fischer garnered five each.

Of the three, only Steinlager is widely available. Fischer, which comes in an outsized, 22-ounce bottle, is from an ancient family-owned brewery, but it has not enjoyed the publicity exposure in this country of its local competitor Kronenbourg.

The Gambian beer is even less known. It is made in the capital, Banjul, "under German management," according to the label. Secretary Gorre-Ndiaye explained that the brewery had been built with government encouragement to provide a domestic beer for tourists. It quickly proved popular with Gambian citizens as well, then last year won a gold medal in a Paris competition. The United States is the first export target, and a recent one. Capital City Liquors began distributing the beer only six months ago.

Beer prices have escalated sharply during the world-wide inflation. At Calvert this week, Steinlager is selling for $15.25 for a case of 24 (12-ounce) bottles. Jul-Brew is $13.95 for 24 (10-ounce) bottles and Fischer costs $13.99 for 12 of the 22-ounce bottles. Smaller-size bottles of Fischer are due here in the fall.

America's infatuation with exotic beers, combined with the appeal of low-calorie products, has moved this country into tenth place as a beer-consuming nation. Beer accounts for about 85 percent of our alcoholic beverage consumption. The ratio is even higher in Mexico (94 percent), Japan (93 percent) and seven other nations.

While there has been a shrinkage in the number of breweries (the number fell from 700 in the late 1930s to 47 in 1977), sales and per capita consumption have grown in the past few years. Advertising expenditures have skyrocketed since Philip Morris purchased Miller in the early 1970s and challenged the sales domination of Budweiser and Schlitz.