The reigning champion, driving for Veloce Racing, set a time of 1m28.728s at the Red Bull Ring on Friday afternoon, making her the only driver to break into the 1m28s.
Rookie Irina Sidorkova was just three-tenths off the pace, with Visser (M Forbes Motorsport), last year’s runner-up, a tenth behind her in third.
Puma-sponsored Marta Garcia finished fourth, with Nerea Marti in fifth and returning driver Emma Kimilainen, driving in the in-house Ecurie W team, in sixth.
Ayla Agren, Belen Garcia, Alice Powell and Abbie Eaton completed the top ten.
Racing X’s Powell was first out on track, with Chadwick’s team-mate Bruna Tomaselli setting an early flying lap with a 1m30.521s.
By the halfway mark, Chadwick led from Marta Garcia and Visser, with a 1m28.728s the quickest time.
W Series Academy drivers Marti and Sidorkova were also jostling for the top spots. The young talents are the only two drivers guaranteed a seat in the championship next year under the Academy programme.
There was almost contact between Powell and Sarah Moore (Scuderia W) at one point, with the pair narrowly avoiding each other in sector 3.
Powell, the current championship leader, won last weekend’s race in Austria, but finished practice in ninth place.
Moore, who took second place in the first round, finished down in 17th after only managing a time of 1m30.177.
Fabienne Wohlwend, driving for Bunker Racing, completed the podium but finished 13th in today’s practice session.
Qualifying takes place this afternoon to set the grid for tomorrow’s race, which lasts 30 minutes plus one lap.