Plummer's bristling Iago - key to Broadway's new 'Othello'; James Earl Jones powerfully moving in title role of Shakespeare's tragedy; Othello Tragedy by William Shakespeare. Starring James Earl Jones and Christopher Plummer. Directed by Peter Coe.

Any attempt to describe the eminently theatrical production of ''Othello'' at the Winter Garden Theater must almost inevitably begin with Christopher Plummer's Iago. The mark of his bristling performance is the degree to which it encompasses the extent, intensity, and depth of the demoted lieutenant's blazing malevolence.

Iago's hatred focuses on the Moor, the commander in chief whom he vows to destroy. But a more fundamental malignity lies in Iago's less noticed expression of misanthropy: ''I never found a man that knew how to love himself. . . .''

Hence Iago's inhumanity. He is prepared to direct it impartially at anyone who can be exploited for his revenge - from the ''sick fool'' Roderigo, whom he fleeces and ultimately murders, to the innocent Desdemona herself. Only young Cassio, with whom Iago falsely accuses Desdemona of having betrayed her marriage , escapes the carnage of the final scene.

With close-cropped hair and military mustache, Mr. Plummer is every inch the model of an upright, parade-ground military man. James Earl Jones's credulous and in many ways unworldly Othello underscores the general's vulnerability to his ex-lieutenant's cunning disguised as candor. An Othello as baffled as he has been cruelly duped cries out his bewilderment at last in the agonized ''Why hath (he) thus ensnar'd my soul and body?'' With this anguished plea, Mr. Jones expresses the mystery of a tragedy about an alien but respected mercenary who has been able to conquer in the gentler art of love but has then been poisoned with suspicion and jealousy toward his honorable and innocent wife. It is a performance at the same time physically imposing, eloquent, and powerfully moving.

Whether or not he had such a thing in mind, Jones's Othello reflects something of what Coleridge wrote in rejecting jealousy as the point in Othello's passion. ''I take it,'' wrote Coleridge, ''rather to be an agony that the creature whom he had believed angelic, with whom he had garnered up his heart, and whom he could not help still loving, should prove impure and worthless. . . . It was a moral indignation and regret that virtue should so fall. . . . In addition to this, his honor was concerned.''

The Winter Garden revival - which began, last summer, at the American Shakespeare Theater in Stratford, Conn. - is serviceably acted in most supporting roles. Dianne Wiest conveys Desdemona's devotion, tenderness, and innocence to an affecting degree. Other principal roles are acted by Kelsey Grammar (Cassio), David Sabin (Brabantio), Aideen O'Kelly (Emilia), Graeme Campbell (Roderigo), Robert Burr (Duke of Venice), and Patricia Mauceri (Bianca).

A handsome arrangement of movable drapes and a high, cross-stage bridge are the principal features of David Chapman's fluid scenery. The renaissance costumes were created by Robert Fletcher and Marc B. Weiss designed the lighting and cloud-effect projections. Stanley Silverman composed the incidental music.

In a program insert, Stratford artistic director Peter Coe, who staged the revival when it first opened, pays tribute to Zoe Caldwell, who has guided things since the tour began in Washington. Mr. Coe notes the changes in cast, set, and lighting, most of which ''have been conditioned by Miss Caldwell.'' For those who saw ''Othello'' at Stratford, Mr. Coe expresses the hope that ''some of these changes will appear for the best.''