THANKS TO THOUGHTFUL direction and a string of sophisticated officials over the last 22 years, the constantly expanding Washington metropolitan area has always been a national leader in regional cooperative efforts -- joint approaches by local governments to problems that know no political boundaries. From the initial chat-and-get-acquainted gatherings of area officials to the scores of complex projects now under the aegis of the Metropolitan Washington Council of Governments, some of the most successful responses have been to changes in living conditions such as employment, transportation, public safety and air quality.

Those subjects will remain among the Council of Government's primary concerns, as indicated in excerpts from the organization's annual report that appear elsewhere on this page (For the Record). But if there is a single critical situation in this region today, it is housing. And the Council of Governments' outstanding efforts over the years in working to preserve and expand the housing supply need even more emphasis in 1980. More and more tenants, displaced by condominium conversions or confronted by rising rents they cannot afford, are desperately seeking relief: only yesterday, some 2,000 applicants for subsidies thronged the city's housing office to bid for 126 grants.And some local politicans, grasping for quick solutions, have supported moratoriums and rent control measures that in the long run contribute to the housing shortage and fail to stem a national problem of inflation.

The COG can point to some impressive projects. For example, in Prince George's County, people with moderate incomes will be able to buy homes through a new revolving fund that will make below-market-rate financing available; in Fairfax County, some new townhouses will be available at below-market prices, and certain developers can qualify for special construction incentives; and in Alexandria, some low-cost apartments will be renovated for low-to-moderate-income families. These projects are supported with federal funds awarded to the region in recognition of COG's efforts.

But the numbers -- of units, of people helped, of dollars in grants -- are woefully low in proportion to the amounts required for significant relief. There is not likely to be any great wave of federal help, either. Still, the individual local governments should continue to assist COG in seeking every federal grant possible for a coordinated regional program of housing assistance.