What could be more daunting for young actors than sharing a stage with pros in challenging material?

You could ask several young women in Olney Theatre Center's experimental summer rep, the Potomac Theatre Project. They're undergrads or recent grads of the theater program at Middlebury College in Vermont. Directors Richard Romagnoli and Cheryl Faraone, both on Middlebury's faculty, and their colleague, director Chris Hayes, put the five young actresses through trials by fire in "Perfect Pie" and a radical redo of Shakespeare's "Measure for Measure."

Cassidy Bree Freeman, 22, plays Isabella in "Measure for Measure," a novice who leaves the convent to plead for her brother's life after he is sentenced to death by the despotic ruler Angelo. When Angelo demands sexual favors for her brother's release, Isabella chooses chastity and piety instead.

"My main goal was to just try and make her refusal of that offer as believable . . . as possible," Freeman says. She feels lucky because Isabella has "just gorgeous speeches . . . and whether you're religious or not, you feel the passion she feels."

In "Perfect Pie," an intensely emotional memory play by Canadian Judith Thompson, six actresses play two central characters as young girls, teenagers and adults. Patsy (played as an adult by MaryBeth Wise) is a hearty farm girl. Marie (played as an adult by Helen Hedman) is an abused child from a poor family.

Jennifer Driscoll, 24, plays troubled young Marie. "I think of her as a little 'creature' in the beginning. She's just so defensive that she doesn't want to be touched or talked to." She "doesn't quite have the tools to exist in an acceptable social manner . . . [but] she becomes more comfortable interacting with Patsy," Driscoll says.

Lily Balsen, 20, plays Marie as a teen. "Emotionally, I think [Marie and Patsy are] pretty similar," she says, with "this very passionate anger." But, adds Balsen, "I felt like I had a little more leeway" than the actresses playing Patsy, because the adult Marie abandons her old identity to become Francesca, an elegant alter ego as divorced from Marie's past as possible.

"It was important for me that the audience saw there were seeds in the teen Marie . . . of what Francesca would become," says Balsen. "Watching [Hedman] and some of her body language, I tried to pick up a little bit on that, but again . . . there had to be a break between the teen Marie and who Francesca would become."

Laura Rocklyn, 22, plays young Patsy. She and Tara Giordano, who plays teen Patsy, focused more on emotional than physical traits. "We didn't want to do anything that would look too contrived," says Rocklyn. "[We] talked about some of the themes that came out in Patsy's personality . . . like her tendency to like to control things."

Giordano, 24, has been acting in Washington since 2001. "I thought it was going to be about getting physical things down and the voice and the movements," she says. Instead she found the key to bridging the three ages of Patsy was that "emotionally they need to be connected . . . but physically, they can be different."

Casting About

If you're an actor, Beverly Marable is someone you need to impress. She has been casting director for the Contemporary American Theater Festival for nearly a decade and before that at Arena Stage, when Doug Wager was artistic director. (The festival, in Shepherdstown, W.Va., continues through Sunday.)

Marable says she studies the four plays chosen by festival Artistic Director Ed Herendeen, then writes a "breakdown" of all the characters and a description of what sort of actor could play each one and whether the right actor could handle two roles in two plays. Her specs are distributed to agents all over New York.

"Tubs and tubs of agent submissions" come back to Marable. "I start reading resumes. And I always go back to front -- resume first, picture last, unless I'm looking for something specific," she says. In early spring, Marable sets up several days of auditions in New York.

Requirements can change with a work in progress, especially a musical such as this summer's "The Rose of Corazon: A Texas Songplay." Riccardo, a character in the three-member Greek chorus-style ensemble, was supposed to be middle-age, but when young Cesar Samayoa turned up, Marable says she thought, "Oh my goodness, listen to his voice!" Such a discovery, "for a new play in particular, it can change the nature of a role," she notes.

For a festival of new plays like CATF, where during rehearsals scripts can get rewritten and songs cut or added, it's best "to have an actor that has as many tools as possible. . . . I give [Herendeen] people with versatility," she says.

Because working at CATF is so demanding, Marable hires mostly experienced Equity actors. There are the versatile regulars like Lee Sellars at this summer's festival, and there are her finds, like Albert Jones in "Flag Day," Perry Ojeda in "Rose of Corazon," Amol Shah in "Homeland Security" and Arielle Jacobs as the title character in "Rose of Corazon."

"Her innocence, her voice, her eagerness, her openness, her directability," says Marable. "It was all there."

Follow Spots

* American Century Theater will hold staged readings Thursday-Saturday of Dorothy and DuBose Heyward's "Porgy," the source material for George Gershwin's opera "Porgy and Bess." Call 703-553-8782 or visit www.americancentury.org.

* Longacre Lea, the summer troupe with a taste for the haute avant-garde, will present Eugene Ionesco's "Man With Bags" Aug. 11-Sept. 5 at Catholic University's Callan Theater. Kathleen Akerley will direct. Call 202-460-2188 or visit www.longacrelea.org.

* Fountainhead Theatre, in association with Keegan Theatre, will present Harold Pinter's "Betrayal" Aug. 14-Sept. 11 at Theatre on the Run in Arlington. Sarah Denhardt directs. Call 703-920-5923.

* The Shakespeare Theatre has had to replace actor Douglas Sills as Macbeth in its season-opener (Aug. 31-Oct. 24). Sills landed a lead in the sequel to the film comedy "Deuce Bigalow: Male Gigolo." He'll be replaced by Patrick Page, who has performed in "The Lion King" and "Beauty and the Beast" on Broadway, played Richard II at the Public Theater and acted in regional Shakespeare festivals.

From left, Tara Giordano and Lily Balsen (in "Perfect Pie") and Cassidy Bree Freeman (in "Measure for Measure") at Potomac Theatre Project.Beverly Marable looks for versatility when casting actors in the Contemporary American Theater Festival.