Now she's using her native "Kiwi" accent for her latest role - which is set in outer space.
In tonight's episode of Battlestar Galactica (10 p.m. on Sci Fi Channel), Lawless plays D'anna Biers, a hard-edged journalist investigating what she believes is a coverup onboard the starship Galactica.
What, you may ask, is an Australian-like accent doing on a show set in a distant part of the galaxy? Galactica, now in its second season on Sci Fi, has established that its characters come from diverse backgrounds. And, hey, if the alien time traveler on Doctor Who can have a British accent, why can't an alien reporter have a Kiwi one?
Lawless had been reluctant to use her native accent in other roles, but felt that it would work well this time.
"Americans are starting to be able to understand me, so it seemed like the time was right and the role was right," she said by phone from the set of her next TV movie, Vampire Bats.
But once she was on the set of Galactica, speaking in her normal voice proved surprisingly tricky. When the cameras start rolling, she is used to doing her performance in an American accent and then shifting back to her normal accent once the director yells "Cut."
"So sometimes, yes, I would go into the wrong accent," she said.
In the show's storyline, her character is given carte blanche to investigate the story that she is working on, much to the chagrin of Galactica's leader, Commander Adama (Edward James Olmos).
"Everybody's on edge just by her very presence," Lawless said.
Though this is a one-time appearance for now, Lawless said she would not be averse to returning to the series.
"I tried to play it that she's kind of got the hots for Adama, because he's like the alpha male and she goes right for the top," she said with a laugh. "Maybe if I come back we can see that relationship come to fruition."