Upon graduating Thomas worked as an artist and taught high school before becoming a part of The Second City, the premiere venue for improvisational theater in Chicago.

While working as an artist and school teacher, she became a waitress at The Second City to earn extra cash for a trip abroad.

A slight, playful romantic comedy, Only You was a departure from Thomas's experience on Hill Street Blues or her subsequent television directing.

The Brady Bunch Movie was a box office hit with domestic ticket sales of $46,576,136, nearly quadrupling its $12 million budget and making it at the time one of the highest-grossing films directed by a woman.

[5] She followed The Brady Bunch Movie with other successes, including Private Parts (1997), Dr. Dolittle (1998), 28 Days (2000), and John Tucker Must Die (2006).

In 2009 Alvin and the Chipmunks: The Squeakquel became the first female-directed picture to gross more than $200 million and made her the most successful woman director up to that time at the box office.