Fullback Walsh was preferred over James Tedesco while Dearden edged out Sam Walker at halfback as both proved highly influential in the emphatic win in Townsville on Saturday night.
Second-rower Jacob Preston was superb with two line breaks and a try ahead of Australia's semi-final clash with either Samoa or Tonga on November 8 in Sydney.
The Kangaroos were sloppy with the ball and their completion rate of less than 70 per cent won't be good enough in the knockout phase.
Australia took a 28-6 lead into halftime after the Cook Islands took it to them in the opening exchanges.
After the break, Australia put their foot down with wingers Jack Bostock and Tom Trbojevic both scoring hat-tricks.
Walsh took a bump during the match on the left ankle he had surgery on late in the season but played through pain to record five try assists and score himself in a quality display.Â
Bench forward Cameron Murray was a late withdrawal with a sore calf but coach Kevin Walters said neither was in doubt for next week.
Walters was impressed with Walsh's five try assists but was not ruling Tedesco out of the frame for next week.
"That's Reece, that's what he brings to the team," Walters said.
"I'll make a decision about the fullback in the next couple of days. James was equally as good last week, he set up four tries last week. We're fortunate with the Australian team and the players we have in our group. Selections are tough.
"It's a good position to be in as coach."
Dearden, with two first-half try assists, combined well with five-eighth Cameron Munster, who assumed the goalkicking duties from Walsh after his foot complaint.
Harry Grant started at hooker and will be the No.9 for the rest of the tournament.
Walsh's subtle double pump put Bostock over for the first try, but the Cook Islands dominated the next 15 minutes
Second-rower Delahia Wigmore, who played this season for Penrith in the NSW Cup, made a barnstorming charge and stood over Kangaroos prop Tino Fa'asumaleaui after running over the top of him.
It was a statement of intent but Fa'asuamaleaui responded with two tries of his own.
Cook Islands rake Rua Ngatikaura crashed over from close range to give the Aitu a 6-4 lead in their first Test against Australia.
The Kangaroos forwards were underwhelming early, but Dearden set up Trbojevic to get Australia in front and they were never headed from there.
Fa'asuamaleaui crashed over and Dearden was provider for centre Kotoni Staggs, before Walsh streaked away after Preston's second line break.
Australia weren't headed in the second half, but the Aitu did not turn it up.
"Proud is the way that describes the way I am feeling," Cook Islands coach Karmichael Hunt said.
"We knew we were up against it but for the boys to go out there and put that first 40 in, I am sure they would have been a little bit shocked at how we came out and what we were able to do."
Cook Islands veteran Brad Takairangi's kicking game at halfback was impressive. It was the 37-year-old's last game for his country in a stellar Test career that included 17 Tests for the Kukis and four for New Zealand.
Takairangi led the pe'e haka for his country before kick-off in an emotional display and Canberra playmaker Ethan Strange had an impressive Test debut off the bench for Australia.
