She has dropped her imaginary gloves on the rehearsal hall floor. She has stomped across the room, her petticoat crackling like windblown drapes. She is searching for an expression to show she is thinking of a sport. The director throws out "tennis," and Sabrina Le Beauf decides "catching butterflies" is more her Rosalind's speed. Then a glance to the distance, past the unpainted drywall of reality to a wistful run through a field of her imagination, brings a dancing light to her face. Minutes later Michael Kahn, director of the Shakespeare Theatre at the Folger and this staging of "As You Like It," suggests a change. He asks her to think about "petitionary," a word she is swallowing. The line comes back like a bullet: "Nay, I prithee now, with most petitionary vehemence, tell me who it is." Not quite, says the director. He wasn't looking for exaggeration. "You mean the emotion," says Le Beauf, and takes a more subtle tack. Here in front of seven people in the bare room of a former grocery on Capitol Hill, Le Beauf is preparing for a star role. The audience over the eight-week run beginning April 25 might total more than 16,000, but that is not even close to the millions who see her portray Sondra Huxtable, the eldest daughter on "The Cosby Show." Still, the moment is hers. And that's why she is here. Because this participant in the "Cosby" dynasty is the forgotten one. The hard fact is that Le Beauf has only appeared in 31 of the 125 episodes, and she is disenchanted, a flat anger casting a shadow across her brown eyes. The actress, who spent seven grueling years at UCLA and Yale learning her craft, wants to change her curious case of visible invisibility. "An actor needs to exercise, the discipline needs exercise to meet the challenges," says Le Beauf, 31, breaking away from Shakespeare to discuss the stage and the small screen. "Working in television you do not have the opportunity most times to do what you are capable of doing. Having been on the show for five years I have not been able to do what I am capable of doing. I feel cheated that 55 million people a week watch something that is not my best work." While she is frustrated, she is also grateful she has learned television at this grand, successful level. Also, she enjoys the financial comforts that have enabled her to buy a Dutch colonial house in Englewood, N.J., and scour the antique shows for her eclectic collection of dogs, rabbits, pineapples and hurricane lamps. Yet, despite the occasional nature of her "Cosby" work, she says she had to fight to be released to work at the Folger. This year, she says, she did only five "Cosby" episodes but says the producers initially told her she couldn't simply be "on call" for the last six episodes. "I couldn't understand why that couldn't be worked out," she says. She says they warned her that if she broke her contract, she wouldn't get paid for the season's remaining six episodes. "I don't feel on this show I am working. You can't tell me that you did 25 episodes and I am in five of them. That is not working. You can't tell me 'we want you here' and 'be here for us,' if I am not going to work," says Le Beauf. In the end Bill Cosby came to bat for her and the work release agreement was amicably settled. She was released from this season's last two episodes, as she requested, but has been called to work on the show next week. Agents for the show and for Le Beauf declined to discuss details of the negotiations. "Maybe it wasn't the right way to do it, but I was basically up against the wall. I went to him and he said, 'Go do the play. I don't see what the problem is. Even if I have ideas for you, you can be written out of them.' He said it is hard enough to get another job, and if you have one, go do it." To Le Beauf, Cosby is a court of last resort and she usually doesn't take problems to him, such as her frustrations with the show. "He is a very sensitive person, but a lot of people with all the frustrations we feel, including myself, don't want to burden him. There are so many people pulling at his coattails with problems and needs. You don't want to go to him unless there is no place else to go. I feel I should be able to work out my own problem. I should learn from him in that he paid his dues, he struggled, he believed in perfection and he had a dream and he deserves everything that he has. I should learn to get through it." In addition to competing with the formidable "Cosby" cast, Le Beauf has this underlying suspicion about her personality. She thinks she's boring. "I still to this day don't see myself as what people think of an actor to be. An actor is someone who comes into a room, they say these funny things and they are hysterical. I don't consider myself a natural entertainer, a natural funny person. I enjoy getting up before people. I enjoy throwing my opinions upon people. But I am not -- in no way -- the life of the party. If you give me something I care about ... then you have something to pull from." She thinks the perception that she is boring might be part of her problems at "Cosby." "You look at something and you say, why is it that they continue to write for this person ... I think if you are excited about something then you write for it. I am not written for. I play the smallest role. I don't feel I make any contribution to the show. So that is why I always say I must be boring. It is my greatest fear in life: I'm boring and they hate me." When she appeared at the Non-traditional Casting Symposium in Washington in September 1987, Le Beauf was considered anything but boring. To illustrate that minorities could play roles that weren't race-specific, Le Beauf and two other actors did a scene from "As You Like It" and Kahn decided right then to do the full production. What Le Beauf discovered in Kahn's acting ensemble was vibrancy. "I was amazed at the amount of energy that came from the actors. I could not believe these people could get up on stage for two, two-and-a-half hours and put out as much as they put out. It was like going to see 'Sarafina!' I wanted the opportunity to do that," says Le Beauf. She returned to see the company's "Anthony and Cleopatra" and "Macbeth." The debate over using actors in roles not written for black, Hispanic, Jewish or Asian characters was rekindled last week when John Simon, the theater critic for New York magazine, wrote a stinging review of Joseph Papp's production of "The Winter's Tale." In the review Simon wrote that Mandy Patinkin looked "like a caricature in the notorious Nazi publication Der Stu rmer," and said of Alfre Woodard that if she "weren't black, one might suspect her of racism; as it is, one suspects her merely of not having the foggiest notion about how to play a classical role." "Time and again he has singled out people of color for criticism," Le Beauf says in response. "It hurts me. As an actor I have to imitate what is life. Life is not homogeneous. It is important for us to represent that on stage, and John Simon isn't helping that cause." "It is all about money and power," she had said earlier. "In theater it comes down to the artistic director and the artistic purpose. I don't see why in theater people cannot just be cast, period. There is no reason. It is inexcusable to me when I go to a play and the play is all white, I say these people had to try real hard to get all white people to do this play." In one part of "As You Like It," Rosalind is banished from her comfortable surroundings and forced to hide in the forest, live off the land and pretend she is a boy. As she becomes friends with Orlando, she has to restrain her own mad love for him. One asset to making her transition between boy and girl characters is Le Beauf's lean, flat contour. Explaining the challenge of playing both sexes, she shows an easy smile and looks coquettish, her wispy dark hair pulled back with tendrils falling over her face and neck. "What Michael is trying to go for in the beginning is that everything is rigid -- you are corsetted, I live in a prison. You have to hold everything in. What he wants in the second act is the freedom. I have not completely found how to manifest the physical differences. I'm trying to give the boy a twangy sound, I'm trying to give Rosalind the speech of the court, a deeper, more melodious voice." What doesn't emerge, either on stage or on television, is the slight trace of Le Beauf's Southern background. To escape the ironclad segregation of Louisiana in the late 1950s, her family picked up and moved to Los Angeles. Her parents divorced, and, until she was about 10, she lived with her maternal grandmother, Sce Ethel Holmes, in south central Los Angeles. Her grandmother was a homemaker. When her mother remarried, Le Beauf rejoined her in suburban Inglewood, Calif. Her mother works for Hughes Aircraft, and Le Beauf has a brother, Graylan Moore, 21, a college student. Her introduction to the stage came through the traditional route of school pageants. She played Cinderella in the second grade. From that time she was immersed in drama. "It was a release and I found great satisfaction, emotional and mental," says Le Beauf. She took a temporary detour into politics when she was president of her all-girl Catholic high school and a Girls State delegate, feeding her needs for a forum, organization and power. At UCLA, where she studied theater arts, Le Beauf encountered her first obstacles to colorblind theater. To combat her personal unhappiness because she wasn't selected for plays and to fight the discrimination, she formed a theater group with other black students and studied directing so she could mount her own shows. In September 1980 she began graduate work at the Yale School of Drama. On the first day the drama students introduced themselves to the faculty and other students who stood up and applauded the newcomers. Le Beauf heard Lloyd Richards, the artistic director of the Yale Repertory, say, "That is the last unearned applause you will receive here." When she finished Yale with a master's in acting, she formed a traveling Shakespearean theater group with two friends. Her goal was to emulate people who belong to the working class, not the glitzy crowd of actors. "I saw John Malkovich in 'Burn This' five times and I sent him flowers. I like things that are daring and outrageous, that people can make a choice that is so far-fetched and outrageous that you fall back in your seat and yet they make it believable," she says. In this category she puts Dustin Hoffman, Dianne Wiest, Alfre Woodard and the South African cast of "Sarafina!" The narrow-mindedness of the entertainment industry, which leads to a lack of material, dampens her outlook for improved opportunities for black actors. Things are improving, she says, a "tiny, tiny, tiny" bit. "Speaking specifically for black women who are my type, we have made some breakthrough. We can sometimes be considered for a film that is not necessarily written for a black person," she says, and lists this group of "acceptable" actresses as including Robin Givens, Rae Dawn Chong, Lisa Bonet and Jennifer Beals. In her first year out of Yale, Le Beauf did a number of auditions, including one for "Cosby," trying to ride the burgeoning popularity of what she calls the "dark, exotic" type. She says she was told she was "too old" to play any of the offspring, but after the first four episodes Cosby decided to add a fifth child to match his personal family. At first, Sondra was a student at Princeton, bringing home her psychology books, dirty laundry and an unsettling boyfriend. Now, they are married and borrowing money from the Huxtables to make ends meet while she stays home with infant twins and he continues his pre-med studies. Ironically, the least-seen child was pivotal to one of the highest-rated show the series has ever had. Last November 50 million people watched the show in which Sondra Huxtable gave birth. "To see America's favorite Dad become a grandfather is probably an event for a lot of people," she says. "That's what it was billed as. It is the most work I have had to do, the most challenging work, but still it didn't feel like it was my episode. It was about how Elvin {her television spouse played by Geoffrey Owens} deals with being a father -- fainting. It was about how grandparents respond, it was about how Dad and Elvin get together. Finally Bill added a scene about he and I because I had never been talked to." To prepare, Le Beauf took Lamaze classes with pregnant actress Kim Staunton and decorated Staunton's nursery, but on the "Cosby" set she felt her involvement was an afterthought. For three of the last six weeks, "Roseanne" knocked "Cosby" out of the No. 1 ratings spot. "Obviously America is turning from one family to another and saying we like this family better. I don't know why that is," she says. Would she leave? She thinks awhile. "That's hard because any actor wants to have a job, wants to be paid for what it is that you do. My favorite line is Dustin Hoffman in 'Tootsie' when he says, 'I will do dog food commercials.' For most actors that's how we feel. So it is hard to say, 'No, I don't want to do that {"Cosby"} because I want to go off and starve.' At the same time you want to have some input. I think in the long run it is important for me to do television, film and, at the same time, when given the opportunity, it is important for me to do theater as well."