"WE MUST CELEBRATE Independence Day from Great Britain -- what should we do?" said very British actor Ian McKellen, to Olney Theater managing director Bill Graham Jr. last week.

"Let's have an old-fashioned outdoor barbecue," Graham suggested. "I'll get some hot dogs and hamburgers, and chips and marshmallows and fried chicken and potato salad and we'll set up a grill out behind the theater."

"Marvelous!" said McKellen, trying to get into the all-American spirit of the thing. "I'll supply the champagne."

So they picnicked with candelabras on the red-checked tablecloths. After the party the candelabras were carried over to the Olney's pool, where McKellen and the Olney actors and crew splashed till the small hours.

Those candelabras came in handy Tuesday night when the power went out at Olney halfway into the first act of McKellen's one-man "Acting Shakespeare" performance. Unruffled, McKellen set the candelabra beside him, sat on the edge of the stage, and continued with an intimate interpretation of the balcony scene from "Romeo and Juliet." During intermission, stagehands lined the stage with all sorts of candles and mirrors, like antique footlights. McKellen reappeared in a white suit, and lit up the stage sans electricity. McKellen's July 19 performance will be sign-interpreted by Robert Hahn.

Hey, look me over: Approximately 650 actors turned up for the annual auditions at Arena Stage sponsored by the League of Washington Theaters. Known as "the cattle call" among participants, the five-day auditions are attended by representatives of 12 theaters, who collect stacks of resume's and photos and observe the actors' two-minute monologues. "Surprisingly," says Horizons Theater director Leslie Jacobson, "you can tell a hell of a lot about an actor in two minutes." For the theaters, it's an opportunity to see new people, and "Many, many people are 'discovered' here," says Arena's Jim Nicola, noting that the exposure the audition affords often results in casting callbacks when production begins again in the fall.

Bart Whiteman, who stepped down this week as artistic director of Source Theater, is far from vanquished. Whiteman, who said this week that he still plans "to take over the world," will be an active force in this year's Source Theater festival, which begins Sunday with a "Rally in the Alley" block party at 4 p.m. Whiteman's murder mystery, called "The Obscure Reign of Gaius Julius Iacoccus," will play Monday through Thursday with Lawrence Redmond's "The Life and Adventures of Holmes and Watson, the World's First Consulting Detectives: An Episode" -- and prizes will be give to audience sleuths who can say whodunit.

To mark the 10th anniversary of Source, Whiteman will direct a revival July 23 to 26 of the double bill that was the origin of Source, John Millington Synge's "In the Shadow of the Glen" and "Riders to the Sea," both of which were performed in 1977 upstairs at the Washington Project for the Arts. Whiteman's new HBW3 Group (for his full name, Harold B. Whiteman III), will present a "literary soiree" of readings August 2, and Whiteman will end the festival August 9 with his one-man performance, "I Am a Washington Actor."

Travel Department: Joan Cushing, better known in these parts as Mrs. Foggybottom, will be subbing this summer for cabaret legend Blossom Dearie at New York's Ballroom. Following Cushing's solo act (called "Lady Sings the News") is a set by Jim Morris, fondly known to Washington audiences for his impressions of President Reagan.

Also leaving home is actress Hannah Weil, who plays Amelia Earhart in Robert McNamara's play "Amelia. . . Last Flight." The one-woman show, which marks the 50th anniversary of the aviatrix's disappearance, takes off in September for London's theater fringe and the international Dublin Theater Festival.

And the Castle Arts Center production of "Clowns," a Polish political satire that had a run here this spring, leaves next month for Scotland's Edinburgh Festival, where it will be a fringe production. The cast includes Karin Abromaitis, Douglas Anderson, Bernie Collins, Lory Leshin and Ritchie Porter.

Last summer, director Phil Setren took Source's long-running production of "Beyond Therapy" to Edinburgh. The show then moved to London's Village Theater and won the London Fringe Award for best comedy, so Setren and actress Leslie Byrne decided to stay. Setren most recently directed Sam Shepard's "Tooth of Crime" starring Jack Bruce, former bass player for Cream.

Stage Superstitions: Irish actor Donal Donnelly, who plays Dr. Watson in "Sherlock's Last Case" at the Kennedy Center Eisenhower Theater, admits to a pre-performance superstition. "Everything I do, through dress rehearsal to opening night, is repeated during the run," Donnelly says. "For instance, I have two pairs of glasses -- one black-rimmed, the other tortoise shell. The black pair never leaves the hotel room, as I wore the tortoise pair during rehearsals. And I have two sinks in my dressing room -- one is virginal, the other is a mess from makeup, etc. Since the show has opened successfully, even if I'm in desperate need of water, I cannot touch that unused sink."

Bulletin Board: Washington playwright Ernie Joselovitz, founder of the Playwrights' Unit, just learned that his play "There Is No John Garfield" will be included in "Best Short Plays of 1989," an annual anthology published by Chilton Press. "Garfield" was premiered this season by Smallbeer Theater . . . Cutting remarks: "Shear Madness," a comic revue about hairdressers that has been running for ages in Boston, sets up shop in the Kennedy Center in September . . . The British Embassy Players recently sponsored the 19th annual Ruby Griffith Award Competition for local amateur theater. In all, 27 theaters were nominated; the Fairlington Players won top honors for their production of "Evita"; runners up included the Reston Community Players for "They're Playing Our Song" and the Colonial Players of Annapolis for "I Do, I Do" . . . Title of the week: The Thunder Thigh Revue brings "Women of Substance" to Baltimore's Theater Project through July 19; then the satirical show about obsessive behavior -- specifically Food, Sex and the Refrigerator -- leaves for three weeks at the Edinburgh Festival . . . While Horizons Theater was on its annual planning retreat this week, someone came up with a novel casting idea: How about a production of "Crimes of the Heart" -- co-starring Fawn Hall, Donna Rice and Jessica Hahn?