It may be all Greek to the Broadway prognosticators, but the biggest hit on Broadway (save The Blue Room ) is Sophocles' 2,500-year-old play Electra. The Zoe Wanamaker starrer just extended its run until March 28, 1999. The production began performances Nov. 19 for a limited eight-week engagement. That stay has now doubled.

The cast for Electra remains the same for Broadway as it was in the NJ McCarter Theatre production, which ran earlier this fall. Wanamaker, who plays the title role, will again be supported by Claire Bloom (Clytemnestra), Pat Carroll (Chorus Leader), Michael Cumpsty (Orestes), Marin Hinkle (Chrysothemis), Daniel Oreskes (Aegisthus) and Stephen Spinella (Servant to Orestes).

The play marks director David Leveaux's first American outing since directing Liam Neeson and Natasha Richardson in the Roundabout Theatre Company's production of Anna Christie.

Electra gave its last performances at Princeton's McCarter Theatre Oct. 4. Soon after the tragedy opened to rave reviews, producers began to discuss a commercial transfer to New York. In the end, the New York move was backed by producers Eric Krebs, Randall L. Wreghitt, Anita Waxman and Elizabeth Peck Williams.

The Wanamaker Electra , adapted by Someone Who'll Watch Over Me playwright Frank McGuinness, originated in London. It was joined on Broadway by another London offspring, David Hare's Blue Room, starring Nicole Kidman, which transferred to the Cort Theatre beginning Nov. 27 after a praised run in London. Wanamaker's credits include stints at the RSC, the Mark Taper Forum (CA) and the National Theatre. Spinella starred on Broadway in Angels In America and the recent revival of A View From The Bridge. Cumpsty starred in Racing Demon and the Roundabout's 1776 revival; Hinkle appeared in a recent Broadway revival of A Thousand Clowns and A Dybbuk at the Public Theatre.

For tickets and information on Electra call (212) 239-6200.