The world’s No. 1 wasted little energy in a brilliant display, winning 6-1 6-3 on Center Court.
Her opponent, meanwhile, was playing in the first grand slam quarterfinal of her career and only managed to settle into the match during the closing stages.
Barty took the opening set with ease in just over 20 minutes and broke serve early in the second set.
With the match seemingly racing to its conclusion, Tomljanovic broke Barty’s serve to give herself a moment’s hope but her compatriot shut the door quickly, breaking back straight away and serving out the win.
“Ajla (Tomljanovic) is an incredible competitor,” Barty said during her on-court interview after the win.
“I’ve played with her a lot, I’ve practiced with her, all Aussies back home are proud of her and it was ( … ) nice to share the court with her today.
“This is a dream come true. I know you hear that a lot but this is my dream and I’m extremely grateful to have an opportunity to live out what I love to do and this afternoon was no different.”
Barty is bidding to become the first women’s singles champion at Wimbledon since Evonne Goolagong won in 1980 and, despite pulling out of last month’s French Open with an injury, she looks well placed to challenge this year.
The 25-year-old’s only grand slam title came at Roland Garros in 2019 but, with many of the sport’s big names no longer left in the draw, this year’s Wimbledon seems as good a chance as ever to add to her tally.
Barty will face Angelique Kerber in the final four after the German comfortably beat Karolina Muchova 6-2 6-3 earlier on Tuesday.
“I love that match-up. She knows her way around this court and I know I need to play well to give myself a chance in that match,” Barty added.
Meanwhile, on Tuesday, Aryna Sabalenka beat Ons Jabeur to reach her first grand slam semifinal. Jabeur had become the first Arab woman to reach the quarterfinals at Wimbledon but fell short of making yet more history after being roundly beaten 6-4 6-3 by Sabalenka.
Sabalenka will now face Karolína Pliskova for a place in the final, after the Czech also reached her maiden semifinal at Wimbledon after seeing off Viktorija Golubic.