A new 17-character play starring Julie Harris, and a rare revival of Frank Loesser's musical Where's Charley, are among highlights of Phoenix Theatre's summer/fall season at the troupe's headquarters in suburban Purchase, N.Y.

* Sonya: Five-time Tony-winning actress Julie Harris stars in Leon Katz's play about the relationship between Russian novelist Count Leo Tolstoy and his estranged wife, Countess Sonya, set on the last night of his life. (July 2-21).

* Below the Belt Richard Dresser's screwball comedy that recently played Off-Broadway. (July 30-Aug. 18).

* Where's Charley -- Frank Loesser 's first musical, written before Guys and Dolls, The Most Happy Fella or How to Succeed in Business without Really Trying. No star announced yet. (Aug. 27-Sept. 15).

* A double bill of one-act comedies, Missing Marisa and Kissing Christine by John Patrick Shanley. Missing Marisa is about two men wrangling over a woman who has abandoned them both. Kissing Christine is about a remarkable first date. East Coast premiere. (Sept. 24-Oct. 13). * The Matchmaker starring Millicent Martin in Thornton Wilder's play that was later adapted as the musical Hello, Dolly!. Oct. 29-Nov. 17.

Phoenix Theatre stages plays at the State University of New York's performing arts center in Purchase, a suburb of New York City.

Single tickets cost $30-$32. Subscribers to the whole season get two plays free. For tickets or information, call (914) 251-6290.