Aprecedent was set 20 years ago for this week's award of the Nobel Peace Prize in Oslo. The Rev. Dr. Martin Luther King Jr. called his 1964 award ''profound recognition that nonviolence is the answer to the crucial political and moral question of our time - the need for man to overcome oppression and violence without resorting to violence and oppression.''
Black Americans whom he led have made immense progress in the ensuing 20 years, although unmet needs remain. Dr. King was one person who did make a difference in the worldwide search for freedom and equality for all mankind.
And now Bishop Desmond M. Tutu has received the 1984 Nobel Peace Prize for his efforts to gain full rights for black and mixed-race South Africans. That the award was given for this work, he said in acceptance, ''says more eloquently than anything else that this is God's world and He is in charge, that our cause is a just cause, that we will attain human rights in South Africa and everywhere in the world.''
The prize, the bishop said, ''has given fresh hope to man in a world that sometimes had a pall of despondency cast over it by the experience of suffering, disease, poverty, famine, hunger, oppression, injustice, evil, and war.''
Bishop Tutu, himself black, joins a distinguished list of individuals, and some organizations, who by being awarded the Nobel Peace Price have been recognized for having had an impact. Theodore Roosevelt was selected in 1906 for mediating international disputes; Willy Brandt in 1971 for striving to build bridges between East and West; Andrei Sakharov in 1975 for his struggle for human rights in the Soviet Union; Menachem Begin and Anwar Sadat jointly in 1978 for ending hostility between Israel and Egypt; and Lech Walesa last year, for his leadership in the struggle of Poland's people for freedom from tyranny.
Bishop Tutu's award comes during increasing protest in the United States against South Africa's segregationist policies. Last week he met with President Reagan, seeking a tougher public US stance toward South Africa. Upon his Oslo arrival the bishop said his prize ''honors all those very many people down through the years who have committed themselves to a struggle for justice and peace and reconciliation in our land.''