He is a handsome, charismatic, and charming British teen, who is an old family friend of Ivy Sullivan. He moves in with Ivy and her mom in the Season 3 premiere, citing having graduated the year before with mediocre marks and being unable to get into a college of his choice. He thinks a year of PG (post-grad) work might help his chances and decides to stay with Ivy and Laurel for his time in Beverly Hills.
Ivy's mother ruined his parents' marriage, and so Oscar seeks revenge by having an affair with Ivy's mother and then sleeping with Ivy, which causes a rift in their relationship. He then shows interest in Naomi, and helps to expose Miles Cannon's lies. He is portrayed by Blair Redford.
Oscar is introduced in the episode Senior Year, Baby, as a family friend of Ivy's who stayed with them over summer, after Dixon left. It is shown that he is very close to Ivy and has known her for a long time, making Dixon give a dislike to him.
However, after making it evident that he understands Ivy and Dixon's relationship and won't interfere, he becomes accepted in the friend group. But, after Dixon breaks up with Ivy, Oscar expresses his feelings toward Ivy to her (which later turn out to be false) and they end up sleeping together.
Ivy regrets it and gets back together with Dixon, but after telling him about what happened, they break up again. Ivy, heartbroken, gets even more upset when she learns about her mother and Oscar's affair. This was all part of Oscar's plan to seek revenge on Laurel, although she points out that this hurt Ivy more than anyone. After that reveal, he moves out of the Sullivan household, and moves into a hotel room. The next day, Oscar apologizes, but Ivy doesn't accept it.
In Holiday Madness Oscar tries to pursue Naomi, who truly helps him grow as a person. He recommended the two go streaking, but little did he realize that she and Ivy were planned to humiliate him in the Country club pool. Despite his embarrassment, he continued to pursue Naomi, who eventually warmed to him but later declined to go out with him because she valued her friendship with Ivy too much to give up on him.
Oscar was never seen, mentioned, or heard from again after Holiday Madness, so it's presumed he focused on his studies and graduated a semester early, allowing him to move back home to attend University there.