MISS JULIE - At St. John's Church, 1525 H Street NW, through May 12. Performances are Wednesdays through Saturdays at 8:30. Tickets are $3.50. For details call 332-5061 or 347-8766.

The Source theater company of Washington has everything but the stage it needs and the audiences it deserves.

This fine company of non-Equity actors is not "little theater," for it has none of the amateurism or preciousness that term often implies.

Neither can it be called "experimental" theater, except in the sense that Source is testing whether Washigton audiences will sit on seats that are not plush to watch plays that are not cast and produced out of New York.

Apart from money, Source's main problem is that it is such a movable feast. The latest move was to St. John's Church at 1525 H Street NW (facing Lafayette Park), where distressingly small audiences are being treated to Strindberg's "Miss Julie" at a shockingly low admission of $3.50.

For a playwright who was nuts, wrote in Swedish and tended to be topical, Strindberg wears awfully well. He invented modern theater almost singlehandedly, and this 1888 play about the dalliance and mutual destruction of a semi-noble lady and her semi-servile servant is less dated than, say, "A Streetcar Named Desire."

Bart Whiteman, founder and leader of Source, plays the leading role as a valet whom Miss (a better translation is "Lady") Julie teases and then succumbs to. I thought he brought too much power to the role, was too proud and bold for a gentleman's gentleman, and resisted his interpretation throughout the performance. Over the following few days I changed my mind, mainly when I realized I had been thinking about his performance again and again; it has been a long time since I have been so engaged by an actor. Whiteman as valet is not too big for the part, the character is too strong for the tiny room in which it is played.

Janet Stanford as Lady Julie has the same problem: her part calls for more than a little histrionics, some of them in Whiteman's lap and all of them in ours, so close are the seats to the stage.

Laurel Allen, playing Kristen the cook, is the only leading character with room enough for her role. Playing a servant fiercely content with her lot, she provides the quiet moral center around which the lady and the lackey dissolve.

The strangeness of sitting cheek by howl with the actors is overcome by the opportunity of studying their craftsmanship from square one. "Miss Julie" is topflight theater at bargain-basement prices.