1989–2002 Oleynik began acting in a
San Francisco production of
Les Misérables in 1989 after seeing an audition ad in a newspaper when she was eight years old. After appearing in the musical, she was referred to an agent by her
Les Misérables co-star,
Rider Strong, and began to take formal acting lessons. becoming quite a favorite among the child and teen audiences and turning Oleynik into a
teen idol. During the show's heyday, children who met Oleynik (and were too young to understand special effects) would often ask her to "morph" for them. Rather than try to explain things, she would quickly glance around, then tell them, "Not here – everybody would see!". Oleynik reprised the role in an
All That sketch, although the name was changed to "Alex Sax". She later made an appearance in the 100th episode of the show. In 1996, she made a cameo on the series
The Adventures of Pete & Pete as a nurse at the beginning of the episode "Dance Fever". Also during her time on
The Secret World of Alex Mack, she played Dawn Schafer, one of the lead characters in the 1995 feature film
The Baby-Sitters Club (1995), opposite
Rachael Leigh Cook and
Schuyler Fisk, and appeared in several episodes of
Boy Meets World as Dana Pruitt, the girlfriend to Rider Strong's Shawn Hunter. She also wrote an advice column for
Tiger Beat magazine, and was involved in Nickelodeon's
The Big Help charity,
Hands Across Communication,
Surfrider Foundation and the ''
Starlight Children's Foundation''. After
The Secret World of Alex Mack ended its run, Oleynik had a starring role in the film
10 Things I Hate About You as Bianca. The film was released in April 1999, and did fairly well at the box office, grossing a total of $38 million domestically. From 1998 to 2000, Oleynik appeared in twenty-one episodes of the
NBC series
3rd Rock from the Sun as Alissa Strudwick. During 2000, she also appeared in two
independent films:
100 Girls (opposite
Emmanuelle Chriqui,
Katherine Heigl and
Jonathan Tucker) and
A Time for Dancing (opposite
Shiri Appleby); neither film received a theatrical release in the United States. Oleynik had a supporting role in the independent drama film
An American Rhapsody (2001), opposite
Nastassja Kinski and
Scarlett Johansson, which follows a young woman whose parents are forced to leave her behind in Communist
Hungary while they flee to the United States.
2003–present Oleynik had a supporting part in
Bringing Rain (2003), a low-budget teen drama starring
Adrian Grenier and
Paz de la Huerta, which premiered at the
Tribeca Film Festival. In 2005, she appeared as a guest star on the series
Malcolm in the Middle as
Reese's lesbian army buddy who develops a crush on
his mother. Oleynik was cast in a supporting role in the series
Pepper Dennis, which began airing on
The WB in April 2006, but was not picked up by The WB's successor
The CW. The same year, she starred in the independent drama
Pope Dreams. In March 2008, Oleynik guest-starred in episode 13 of
Aliens in America. In 2009, she provided audio commentary for the
10 Things I Hate About You 10th Anniversary Edition Blu-ray. In March 2011, Oleynik started appearing in a recurring role on
Hawaii Five-0 as
CIA analyst Jenna Kaye, until her character was later killed off. She was subsequently cast in the
Ayn Rand adaptation
Atlas Shrugged: Part II (2012), as Cherryl Brooks, a store clerk who becomes acquainted with the protagonist, Dagny Taggart (portrayed by
Samantha Mathis). Oleynik also guest-starred as
Ken Cosgrove's girlfriend (and later wife)
Cynthia Baxter in several episodes on the
AMC television series
Mad Men. In 2016, Oleynik starred in the one-woman show
I Loved, I Lost, I Made Spaghetti at the
Hangar Theatre in
Ithaca, New York. Beginning in 2017, Oleynik starred in the
Off-Broadway musical comedy
Baghdaddy. In 2020, Oleynik starred in the Netflix family comedy series,
The Healing Powers of Dude. In 2023, it was announced that Oleynik was cast as Sylvia in the Nickelodeon comedy
Erin & Aaron. In 2026, Oleynik is set to perform in
POTUS: Or, Behind Every Great Dumbass Are Seven Women at the
Santa Fe Playhouse. ==Personal life==