Among his NATO colleagues, Greek Defense Minister Evangelos Averoff cuts a most unusual figure. He has written a play condemning war and the military - a play that is running for second season in a major theater in Romania, a member of the Warsaw Pact.

Averoff was here this week, plugging another of his literary works with zest almost equal to his passion for politics. He is today one of the four most powerful men in Greece and may be a possible successor to Premier Konstantine Caramanlis.

Averoff, of course, would like to be Greece's premier. "All Greeks would like the job," he says, insisting however that "as long as Caramanlis holds the post I will support him. If Caramanlis decides to retire, then. . ."

He has published 14 books, among them five novels, several collections of short stories and fables, and three historical studies. The latest one, titled "By Fire and Axe," is an account of the 1944-49 Greek Civil War.

Although on a private visit to promote his most recent book, Averoff was invited to dinner by Secretary of State Cyrus Vance and he met with Vice President Mondale and a number of House and Senate members.

"For me," he said, sipping scotch in the lobby of Hay Adams Hotel late one night, "writing is an outlet. I get satisfaction from being able to say a lot of things in a pleasing way."

At 67, Averoff is a slight, grayhaired man with a trim mustache and proclivity for dressy suits. He became a cabinet minister at age 39, and served as foreign minister of Greece from 1956 to 1963. During the seven years of military dictatorship, he opposed the junta but remained in Greece and was briefly arrested.

He delights in telling a story about a book he wrote while in solitary confinement. It has since been published in Athens under the title "Forest of Joy."

"I was writing children's stories for adults," he said explaining how he was using an innocent looking technique to address grim problems that Greeks faced under the military dictatorship. "One evening Major Spanos (of the military police) came to inspect the cell and my writing. He looked at my stories and said to me with disgust, "There are childrens stories," Averoff said chuckling.

"By Fire and Axe" was written "thanks to the dictatorship," he said. He wrote it in French, and the book was published in Paris three years ago. It won the French Academy's Medaille D'Or for 1974.

After the collapse of military rule in the wake of the 1974 Turkish invasion of Cyprus, the new premier, Caramanlis, placed Averoff at the head of the Defense Ministry. It was the toughest assignment at that time.

As a writer and reconter, Averoff has both a sharp sense for dramatic values and a keen psychological in sight into the character of his people. Both were needed for the complex task of reining in the army officers who had gotten accustomed to running the country.

There is a celebrated incident that took place a few days after the civilian government was installed in Athens. The junta officers were still in charge of the armed forces, and the last dictator, Brig. Gen. Dimitrios Ioannides, was still running the military police.

Averoff was fresh at his office in the defense ministry when Ioannides walked in unannounced. Averoff pulled a .45 caliber pistol from his desk drawer and ordered the general out. The gesture put the powerful general in his place. He was subsequently tried and imprisoned for life for his role in the junta.

Apart from his writing, Averoff is an avid agriculturist. He has a farm in Thessaly with "4,000 almond trees that are cultivated under the most modern methods." He even drinks his own wine. Indeed, Averoff once served as agriculture minister for three months and that was, he said, "my happiest experience in government."