The odd man out has been a specialty of British playwright Simon Gray. The central figure of ''Wise Child,'' which introduced Mr. Gray's work to Broadway audiences in 1972, was a fugitive from justice masquerading as a woman. The prize-winning ''Butley,'' which came to New York a year later, concerned a misanthropic, fiercely witty schoolteacher who was destroyed by his own cynicism and contempt for others. In ''Otherwise Engaged'' (1977), a would-be reclusive publisher struggled unsuccessfully to fend off clamorous invasions of his privacy.
''Close of Play,'' which was done Off Broadway in 1981, carried the spectacle of aloofness and isolation a step further. The patriarchal figure to whom his family delivered their confidences was a revenant, motionless and silent. While it puzzled both British and American audiences, the play had much to say about the contrary forces that swirl within a domestic situation, the selfishness that can isolate and the shadows that can haunt relationships.
Mr. Gray borrowed the title ''Close of Play'' from a cricketing phrase describing the state of a match that has ended for the day but will continue on the morrow. Quartermaine's Terms, which has just inaugurated the attractive new Playhouse 91 on East 91st Street here, is a quietly touching comedy set among the groves of academe, one of Mr. Gray's favorite milieus. The title applies ''terms'' to school semesters as well as to the conditions of St. John Quartermaine's contract with life and to his associations with fellow teachers.
The play covers a three-year period in the 1960s and takes place in the staff room of a Cambridge, England, school of English for foreigners. Quartermaine (Remak Ramsay), the odd man out in this small institution, is one of those amiable, rather charming nonentities who can leave a room without creating a noticeable absence. He is a reliable baby sitter rather than an invited guest. He is diffident with a difference, the master of the blank expression and the slow grasp. As one of his colleagues remarks, ''You have an amazing ability not to let the world impinge on you.''
When Eddie Loomis (Roy Poole), the school's co-director, gives one of his pedagogic pep talks, Quartermaine interrupts with unwanted cheers. He doesn't just lose the train of a conversation; he never catches it to begin with. The object of belated invitations, he finds the unaccustomed hospitality confusing and embarrassing.
Drifting in and out of other peoples' lives, Quartermaine becomes the recipient of the confidences that provide the play's comic and dramatic substance. The husband of Anita Manchip (Caroline Lagerfelt) is having an affair with the editorial assistant on the artsy literary magazine he is publishing. The daughter of senior teacher Henry Windscape (John Cunningham) suffers a breakdown after failing her exams.
Morose Mark Sackling (Kelsey Grammer) is sacrificing his marriage and family to the novel that will never be published. (Creative frustration in the teaching profession is a theme Mr. Gray has touched on before.) The clumsy provincial, Derek Meadle (Anthony Heald), finds both romance and permanent employment in the course of his scholastic association. Melanie Garth (Dana Ivey) loses her ailing mother and discovers religion with a fundmentalist sect. ''Quartermaine's Terms'' ends on a falling note as the passing of the school's co-director leads to a consequence the unwary instructor has never anticipated.
The central role makes exceptional demands on Mr. Ramsay. He meets them with a performance of quiet understatement and touching sincerity. Mr. Gray has given Quartermaine one flight of eloquence that suggests the capacity for feeling within an apparently unremarkable man. Mr. Ramsay delivers it movingly. But in terms of the school, Quartermaine's appealing decency, his concern for his colleagues and their children, and his good intentions cannot compensate for his increasing professional inadequacies.
The balances of the play - the mingling of staff-room chitchat and the disclosures of problems beyond the classroom - are admirably preserved in the production staged by Kenneth Frankel. Notwithstanding their personal crises, the faculty members discharge their academic responsibilities with some dignity and dedication.
It can be argued that Quartermaine's negligibility leaves a certain empty space as far as the audience is concerned. Though not baffling, like ''Close of Play,'' Mr. Gray's latest view of academia does present a central figure whose very negativeness is his raison d'etre. There are also one or two minor problems. Some of the comedy tends to predictability (like Henry's unfinished holiday recital), while the satiric comment can suffer from repetition (all the jokes about Britons' resolute inability to get other peoples' names). But even here, the dialogue is always believable, and it is often very funny.
So an evening with Mr. Gray's new odd man out is an evening well and enjoyably spent. Eavesdropping on the conversation in designer David Jenkins's unostentatiously hospitable staff room offers a pleasant and instructive glimpse of teachers offstage. Bill Walker designed the costumes; the lighting is by Pat Collins. ''Quartermine's Terms'' was presented earlier by the Long Wharf Theater , New Haven, Conn.
As for Mr. Gray, Quartermaine can scarcely be his final odd man out. The supply is inexhaustible. The world is full of them. And he is sensitively tuned to their wavelengths.