STERLING VINEYARDS, set like a white monastery on a hilltop in northern Napa Valley, is a fitting symbol of corporate wine-making in California. Founded in 1964 by two Englishmen, a former journalist and a former fighter pilot, Sterling amassed considerable vineyard land before the boom in California wine- making and early acquired a reputation for quality wines, among them merlot and cabernet sauvignon. The wine made money for Sterling and so did tourism. A chairlift was installed to carry day-trippers from San Francisco and elsewhere up to the winery's spectacular overlook, and the entire wine-making operation became part of a self-guided tour. Now every year about 200,000 people pay $4 apiece for this privilege and a taste of Sterling's varietals -- cabernet sauvignon, merlot, chardonnay and sauvignon blanc. Many take wine home with them.

Sterling was sold in 1977 to the Coca-Cola Co., part of a highly publicized move into the world of wine by that company. "The executives drank Coke as an aperitif," says Sterling's current president, Thomas Ferrell, "but they loved our reserve cabernet." Apparently they didn't love the big capital outlays for new equipment, the marginal profitability and the long-term planning involved in making and selling wine at the so-called high end of the market. In 1983 Coca-Cola sold Sterling and its other wine interests, with more publicity, to Joseph E. Seagram & Sons, one of the world's largest producers and marketers of wine and spirits. Seagram was a family firm with a tolerance for the costs of keeping Sterling in the position to which it had become accustomed, according to Ferrell, who was hired by Seagram from Inglenook, where he was the winemaker. "When I ask for the finest cooperage," Ferrell says, "they can't say no" because premium wineries have collectively raised technical standards.

Sterling is also planning to buy more vineyard land, although it already owns close to 1,000 acres of grapes. The best come from Diamond Mountain, visible from the winery's terraces. They are blended into Sterling wines because until recently Diamond Mountain fruit has been considered too assertive to be bottled on its own. Now Sterling is releasing an unblended cabernet, its first vineyard designation, Diamond Mountain Ranch. The '82 is intense and berryish, with cedar overtones and big, characterful fruit. It costs $15, a reasonable price for a well- made mountain cab, and a full $7 less than Sterling's more austere reserve cabernet. "We try to price our wines as high as we can," says Ferrell. Indeed, no one has ever accused Sterling of charging too little.

Seagram performs the marketing and distribution for other quality winemakers, among them Francis Mahoney, president of Carneros Creek in southern Napa. In the early '70s, Mahoney bought a dozen acres in the Carneros district, which has a climate moderated by San Francisco Bay and a reputation for concentrated chardonnay and some of the best pinot in America. Also marketed by Seagram are the estate- bottled cabernets and chardonnays of Lambert Bridge winery in Sonoma County, wines made from 80 acres of vineyard owned by Gerard Lambert of the St. Louis pharmaceutical family, another sort of corporate connection in the layered world of California wine.