SPAIN GROWS MORE WINE grapes than any other country, yet until recently its exports have not begun to match those of France and Italy. Spanish vineyards produce fewer grapes per acre, but they have unusually high flavor concentration. Traditional Spanish wine-making means a lot of aging in wood. The introduction of modern techniques, and some restraint in the use of oak, have resulted in more uniformity and some beautiful revelations for those unfamiliar with the quality and cost of Spanish wine.

Given the ridiculously high prices in Burgundy and Bordeaux, the prudent drinker of good reds should look farther south -- in this case to Rioja, in northern Spain. Named after the Oja river, a tributary of the Ebro, Rioja extends southeastward from the rocky hills around the town of Haro to the dry environs of Alfaro. More than 100,000 acres of vineyards flourish here, producing the most famous Spanish wine other than sherry. The best comes from the higher elevations of Rioja Alta and Rioja Alavesa, rich blends of garnacha, tempranillo, graciano and mazuelo. Those grapes may sound alien to lovers of cabernet and pinot noir, but it was to Rioja than many French winemakers and negotiants turned during the phylloxera epidemic a century ago.

Wine-making in Rioja today owes something to the de-stalking and aging methods of the Bordelais and to the high-tech methods of California that produce cleaner, fruitier wines. Those of Rioja have two advantages for the consumer. One is price. Although they have recently gone up, and the value of the dollar is still going down, the wines remain relatively cheap. The other is that the wines of Rioja usually have several years of age when released. Red wines are generally drunk too young in this country; if you like the taste of really old wines, you can buy a faded Rioja of considerable longevity for less than $20. That is about what you would pay for a second-growth Bordeaux bottled last year for drinking after the turn of the century.

The best recent vintages for Riojas are '70, '78 and '81. Also good are '73, '76 and '80. The word "Cosecha" on the label simply means "harvest," or vintage. Reserva means the wine has been aged in oak five years or more, and the Gran Reservas even more, although the terms are relative. Even the ordinary Riojas get a couple of years of wood. Don't be put off by chicken wire wrapped around some of the bottles; often those contain wine of finesse and wonderful length.

There are several producers of good Riojas now available here. The wines of Compan ia Vini'cola del Norte de Espana ("Cune") and of Olarra have been discussed. Those of La Rioja Alta -- a company name, as well as that of a region -- include the Vin a Ardanza '76 Reserva, with body and depth, for about $8. Slightly more expensive, elegant without the weight, is La Rioja Alta's '73 Reserva 904. The '73 Berberana is lighter still, but very flavorful, and costs only $7.

There are several good '78 Reservas for about Beronia, Rioja Vega, Monsieur Henri's Gran Condal and La Rioja Alta's Vin a Arana. The '78 Vin a Ardanza Reserva is a bargain at $7. A slightly coarser but appealing and full-bodied Rioja is the '80 Faustino V, in a curious opaque bottle with a renaissance label -- $3.50, and ready to drink.