When Young and the Restless premiered in 1973, the two central families were the wealthy Brooks and poor Fosters. Of the four Brooks daughters, the eldest, Leslie, was a serious, very accomplished pianist, although she was very introverted and dateless because music had consumed her entire life.

Leslie was in her mid-twenties when her father Stuart befriended a penniless drifter named Brad Eliot and gave him a job at The Genoa City Chronicle, of which Stuart was the owner and publisher. Leslie fell in love with Brad who encouraged her to come out of her shell and enjoy a very successful career as a concert pianist. Leslie's 21-year-old sister, Lorie, who had always been jealous of Leslie because Stuart had spent so much time nurturing Leslie's talent, returned home from college in Paris where she had led a wild life of sex, alcohol, and drugs. Unable to spark any interest from Brad, Lorie started intercepting their letters and phone calls while Leslie was on tour. Lorie managed to convince Brad that Leslie was no longer interested, and convinced Leslie that she had seduced Brad. As the thought of Brad and Lorie making love haunted Leslie, she had a nervous breakdown, freezing at the piano during a concert in New York City. After being led off stage by her mentor, Maestro Fautsch, Leslie wandered through Central Park, her purse was stolen, and she wound up institutionalized for weeks with no memory in a ward with a few other mentally disturbed women who taunted her mercilessly. Eventually her doctor discovered who she was from a publicity photo and notified Stuart, who flew to New York and rescued Leslie.

Stuart and his wife Jennifer secretly supported Leslie through her recovery in a sanitarium near Genoa City. Meanwhile, Lorie became engaged to Brad. After months of therapy Leslie was released. When Brad found out what Lorie had done, he broke up with Lorie, and he and Leslie got back together. Lorie quit her job at the Chronicle and published her first book, which Stuart editorialized as "a disgusting piece of trash". With Brad's encouragement, Leslie bought Pierre's Restaurant and turned it into The Allegro, a nightclub where she could perform without having to travel. Stuart and Jennifer spent many evenings at Allegro, proud of their talented daughter who was also singing there.

Lorie had dug up Brad's past, and she exposed it once she was no longer in his life. Brad had been a Chicago neurosurgeon/psychiatrist who had gone against hospital rules to operate on his own son who had died on the table. Brad had been so distressed that he had left Chicago, leaving his practice, his parents, and his girl friend Barbara Anderson behind. His wrecked and burned car had been found later with a body inside which had been burned beyond recognition, and he had been declared dead. Leslie ended up healing Brad by getting him to talk to Barbara and other neurosurgeons who convinced him that he had done all anyone could have for their son, and that their son's death was not Brad's fault. Leslie also arranged a reconciliation between Brad and his parents. Brad and Leslie then married. They honeymooned in Palm Springs where the Mid-America Symphony was performing. Brad had gotten tickets and arranged a meeting with Maestro Fautsch, who talked Leslie into resuming her career as a concert pianist.

While performing in Paris, Leslie ran into old friend Lance Prentiss, wealthy eligible bachelor and co-owner of Prentiss Industries, who lived in an estate not far from Genoa City on Lake Geneva. Leslie would often spot Lance in the audience as she toured the world performing, and he would meet her afterward for dinner. Lance finally revealed to Leslie that he was in love with her. But although their marriage was occasionally rocky, Leslie demurred, saying that her heart belonged to Brad. The kind and forgiving Leslie set Lance up with her younger sister, Lorie. After being lavishly romanced by Lance with intimate dinners all around the country and the world, Lorie gave in to his charms. Eventually when things began to get serious between them, Lance explained that his mother Vanessa lived at the estate, and was a recluse who wore a veil over the lower part of her face. The veil hid the scars incurred years ago when she had rescued Lance from a fire which had been accidentally started by his younger brother Lucas. Vanessa had been peering through peepholes in the walls of the mansion for years, and had observed Lance with Lorie and other women before her, including her sister Leslie. Lance and Lorie were married on the spur of the moment during a trip to Lake Tahoe, and Lorie moved in with Lance and Vanessa. Vanessa was displeased by Lance's choice of Lorie, whom she viewed as she did all young women in Lance's life, as a potential threat to her having her son all to herself. Although Vanessa was always gracious in front of Lance, she was spiteful to Lorie when he was not around.

Later that year Brad discovered that he had chronic neuritis and was going blind. Rather than let Leslie give up her career for him, he kept it a secret and made Leslie fall out of love with him, then asked her for a divorce. But when Brad discovered that Leslie was pregnant, he told her the truth, learned to read Braille, and they agreed that Leslie would never give up her career for him. After Brad accidentally hit Leslie in the stomach with a suitcase which caused her to miscarry, Brad filed for divorce and left town. Brock Reynolds helped Leslie get over Brad and proposed with a ruby ring, but she gently told Brock that she wasn't ready. Brad later returned, his eyesight restored by a risky operation, but Leslie rejected him, and he again left town.

While Lance and Lorie were honeymooning, Vanessa invited Leslie to visit her. Vanessa let Leslie know that she would have preferred the more refined Leslie for her son, but Leslie defended Lorie. Leslie pointed out that Lorie was a really a good person who had even scrapped her second novel, In my Sister's Shadow, in deference to Leslie, because it told the story of Leslie's recent nervous breakdown. Vanessa hired a private detective who discovered that Lorie's book had not been scrapped, but instead it had just been published. During one of their many altercations, Lorie accused Vanessa of only refusing plastic surgery to hang onto Lance. Vanessa countered that she would tell Lance of Lorie's new book, if that accusation ever got back to him.

Lorie tracked down Lance's brother, Lucas, in Hong Kong, and persuaded him to return home, hoping the diversion would stop Vanessa's obsession with Lance. Lucas had disappeared shortly after the fire, once he knew that his mother would survive, because he felt guilty for causing the fire and her disfigurement. Vanessa welcomed Lucas home with open arms and gratitude to Lorie. Vanessa assured Lucas that she had never held him responsible, and he was able to convince her to finally have the plastic surgery that removed her scars.

Leslie's father, Stuart, found out that Lorie's book had been published. He berated Lorie, then broke the news to Leslie who was devastated and swore that she would never forgive Lorie. Leslie, later while on a concert tour, found herself hounded by reporters anxiously seeking the tawdry details about her nervous breakdown and time spent in a sanitarium. Leslie became so upset that she nearly suffered a second breakdown. When Lance heard what his wife had done, he lashed out at Lorie, and then flew to Denver to meet Leslie to give her emotional support. Leslie had decided to cancel the remainder of her tour, but with Lance there by her side, she went on to her next concert. But when Leslie surveyed the audience, imagining them all knowing about her past, she froze, and then ran off the stage. Lance comforted Leslie, and they returned to her hotel suite, where they ended up making love. The following morning, Leslie felt so guilty that she encouraged Lance to patch things up with Lorie. They kissed goodbye, and Lorie witnessed it. Thinking that Lance was now committed to Leslie, Lorie immediately went on the road to promote her new book.

Leslie discovered that she was pregnant, but just as she was about to tell Lance that he was going to be a father, Lance told her that he was going to reconcile with Lori. Reeling from Lance's decision, Leslie went on to her next concert date in Seattle. Lucas followed, who by then had fallen in love with Leslie. After Leslie confessed that she was carrying Lance's child, Lucas sympathized and proposed. Leslie and Lucas declared that they would never tell Lance that the baby was his, and they were married. Leslie's mentor, Maestro Fautsch, let them live in his villa in Switzerland to keep the baby's birth date a secret. Leslie gave birth to a healthy baby boy, whom she named Brooks Lucas Prentiss.

Meanwhile, Vanessa, as part of her latest scheme to break up Lance and Lorie, invited Lucas to join Prentiss Industries. Once her baby had been born, Leslie offered Lucas his freedom, but Lucas wanted to stay married to her. They returned to Genoa City, and Lucas went to work with his mother. Vanessa had been transferring stock into Lucas' name until they were able to remove Lance as president, and Lucas took his place. Lucas felt guilty, and offered Lance the position of heading the European office in Paris. Lance refused, and he and Lorie moved from the estate to a penthouse in Genoa City. Before they left, Vanessa confided to Lorie that the only way Lance would be reinstated was if Lorie divorced him.

Lucas went to join Leslie and Brooks on her concert stop in Australia. But Lance was already there visiting Leslie. Lucas spotted them together having dinner, and assumed they were in love again. But Lance had actually been telling Leslie that he intended to commit to Lorie and accept Lucas' job offer in Paris. So when Lance later accepted the Paris job, Lucas rescinded it and offered him a job heading up their dangerous Santa Domingo office instead.

Although Leslie appreciated the support that Lucas gave her, she realized she didn't really love him and they divorced. Lance convinced Leslie and Brooks to live at the penthouse with him and Lorie. But after an upsetting confrontation with Lorie, who correctly guessed that Lance was really Brooks' father, Leslie suffered another nervous breakdown and disappeared, leaving Brooks behind.

Wandering aimlessly with amnesia in another town, Leslie found herself at a bar. Jonas, the owner, was immediately drawn to Leslie, who told him that her name was Priscilla. Jonas turned her from a brunette to a blonde and she began playing the piano and singing at his club. Leslie became so happy and in love with Jonas that she no longer cared about discovering her past. But when her doctor told her that she had had a baby not long ago, Jonas became worried that there was a child growing up somewhere without a mother.

As Lance became more and more depressed without his work, Lorie decided to get him to divorce her, and Vanessa let Lance come back to Prentiss Industries giving him the European division office to run from Paris.

Lucas and Jonas met when both went off to fight the dictator of San Leandro. Lucas discovered "Pricilla" as a stowaway on the jet, but Leslie didn't recognize him, and it was obvious that she was in love with Jonas. After their successful adventure, they all returned to Genoa City. "Pricilla" met Lorie, but did not recognize her either. Lorie and Lucas told Leslie who she was and who they were, but Leslie became confused and overwhelmed. Lorie worried that Leslie would soon regain her memory and demand custody of Brooks. But Leslie explained that she couldn't be a proper mother to a child she did not remember, and she gave full custody of Brooks to Lorie.

As Leslie and Jonas were about to leave the Allegro for home, Leslie encountered Maestro Fautsch who persuaded her to play for him. Leslie was amazed as classical music flowed from her fingertips. When she realized how truly gifted she was, she decided to stay in Genoa City, and she persuaded Jonas to stay as well, and to take over her club, The Allegro, which he renamed Jonas's. After falling and hitting her head, Leslie regained her memory and recalled her love for Lance and that he was the father of her son. Leslie filed for custody of Brooks, but lost him to Lorie because she was the only mother he had ever known. Vanessa suggested Leslie tell Lance that he was the father of Brooks, so she, Lance and Brooks could be together. But in the end, when Lance discovered that Brooks was his son, he rejected both Lorie and Leslie for keeping it from him. And when Brooks refused to have anything to do with Lance, he returned to Paris alone.

Leslie then became involved with Attorney Robert Laurence, and they made plans to marry. But when Robert's ex-wife Claire, who was institutionalized, was given a drug that finally worked that brought her back to reality, Robert returned to her to try to rebuild their family with their daughter Angela. Leslie went back to touring in Europe, and was only seen again when she and her sisters returned to Genoa City to attend the wedding of Victor Newman and Nikki Reed in 1984.

In March of 2018 Leslie and Lorie Brooks returned to Genoa City for the Walnut Grove Centennial Reunion, and were sitting at the bar of the Genoa City Athletic Club as Jill walked in. Referring to her as their "former stepmother from hell", they exchanged barbs and mentioned that the school was honoring their father by naming the journalism lab after him.

In 2019, Jack and Traci Abbott while doing research to write the Abbott Family memoirs, discovered that Stuart Brooks and their mother Dina had a one night stand in high school which produced a baby boy. Apparently Stuart never knew since Dina went abroad for a year, and the baby was adopted by Margaret and Ralph Vanderway in Chicago. They named him Eric. Eric grew up to be a union delegate for the teamsters, had a family, but died from a heart attack when his son Theo was 15 years old. Theo landed in Genoa City as an adult. The Abbott family was shocked to find out that Theo was family, and DNA proved it. They gave him contact information for his half-aunts Leslie, Chris, and Peggy.

In spring 2021, Victor and Nikki Newman attended the Leslie Brooks concert in Florence to celebrate Nikki’s birthday. Later in October, Leslie performed at their daughter Victoria’s wedding to Ashland Locke at the Newman palazzo in Milan. She played everything from concertos to jazz, and accompanied Genoa City singer Tessa Porter as Victoria walked down the aisle.