The Wolf Trap Opera's solid, idiomatic production of Marc Blitzstein's "Regina," which debuted Friday night, was successfully repeated with an alternate cast the next evening.

This musical setting of "The Little Foxes," Lillian Hellman's searing drama of greed and hatred in the turn-of-the-century South, is particularly demanding for the performers. To bring it off the acting has to be as good as the singing. Because the dramatic material is so familiar, both from the recent production at the Kennedy Center and from repeats of the classic movie version with Bette Davis, a singer cannot get away with just coasting along on stage.

That is not to say the soprano's acting in the opera's title role must match Davis' or Elizabeth Taylor's, but she cannot afford to be an embarrassment by comparison. Lynn Beckstrom was certainly nothing to apologize for. Through much of the first act she maintained at least a suggestion of the venom that motivates the character, and her singing of Regina's splendid first act aria was powerful. But by the third act, where she has her crucial confrontation with her dying husband, Horace, her performance was running out of steam. Regina, the Lady Macbeth of Hellman's plays, became altogether too casual.

Also, Beckstrom faced a problem not unlike the one that threw Taylor's Regina a bit off base. Beckstrom was consistently out-acted and outsung by the actress in the role of the tender, pathetic Birdie. In the recent play, Birdie was Maureen Stapleton, in a blazing performance. Saturday night, Birdie was soprano Barbara Hocher, who brought considerable splendor to the Wolf Trap company this summer as Fiordiligi in the production of Mozart's "Cosi fan tutte."

The first half of the third act is the opera's extended span of greatest musical intensity and is dominated by Birdie -- first in a quartet in which she is trying to console Alexandra, the distraught daughter of Regina and Horace, and then in the extended scene where Birdie recalls her happy past before she was victimized by the rapacious Hubbard family. Hocher has a large, resonant voice that she uses with considerable finesse. Her acting put all others in the shade, and she was rewarded was a long ovation at the scene's end.

The only holdover from opening night was Anita Berry as the servant Addie. She sang and acted with warmth and beauty. Lisbeth Lloyd was a fine Alexandra; she sang with particular beauty in the opera's last aria.

The leading men did less well, with the exception of James Dietsch as Ben. Joseph Pate made Horace into a pasteboard character.

The orchestra, under Richard Woitach, rendered considerable justice to Blitzstein's strong score.