At times it seems as though Richard Schechner and The Performance Group may overwhelm Brecht's "Mother Courage" with their elaborately simple production details, but ultimately it is the play, not simply Mother Courage herself, which burns through.

From their Performing Garage at New York's 33 Wooster St., Off-Off-East of Greenwich Village, the group has reconstructed its environmental theater of wooden planks and iron scaffolding on the flat floor of American University's Clendenen Theater.

There will be further performances tonight, and next Thursday through Saturday at 8 P.m. Anyone interested in experimental theater should not miss this, seen briefly in the same setting two summers ago.

In a curious, wholly confident way, James Clayburgh's environment of ropes, pulleys, old tires and single props, which represent whatever the script's words may turn them into for a moment, serves the chaos Brecht demands for this slice of the 15th-century's Hundred Years' War. One can scrunch to the edge of a platform or walk about or climb ladders to watch.

Yet through it all, the war, Mother Courage and Her Children are inexorably with us, surviving. Often a production of this play winds up with our admiration of Mother Courage as the residue. In these surroundings she is more victim than heroine, which is what Brecht always wanted. Joan MacIntosh is mmensely careful to keep the character from overwhelming the play.

Lecny Sack's perormance of the mute daughter is exceptionally imagined, her moans and whimpers after the rape scene a kind of impersonal, universal expression of emotion, not designed to move but moving nonetheless.

Sections of the play, without Clayburgh's hauting ropes and with only what lighting is in the room, will be given Monday through Friday noons next week in the Labour Department cafeteria. The result will be quite different, depending a good deal on the performers' weakest quality, clarity of speech, but the informality should serve Schechner's basic purpose.