NRLW heavyweights Brisbane will miss the finals series for the first time in the competition's history after a 28-16 loss to Parramatta, who have surged from the bottom of the table to the play-offs.
Brisbane won the first three NRLW premierships but finished the season with 1-4 record to complete a fall from grace that started with their early exit from last year's finals.
In the second game of the NRLW triple-header at Central Coast Stadium, the Sydney Roosters defeated Gold Coast 38-12 to finish the regular season undefeated and become the first side other than Brisbane to clinch an NRLW minor premiership.
The win also confirmed the end of Gold Coast's season, meaning neither Queensland team will feature in the semi-finals at Brisbane's Suncorp Stadium next week.
Heading into the last round, the Broncos, Gold Coast and Parramatta all had chances to lock up fourth place and a finals spot.
The Eels were the only winless team of the three but by muscling up to beat the Broncos by more than six points were able to leapfrog the Queensland sides on points differential.
Forwards Kennedy Cherrington and Simaima Taufa spearheaded the team's physical effort, running for more than 250 metres each and scoring late tries that confirmed the most memorable win of Parramatta's short NRLW history.
"The performance was something I'm really proud of and something I'll remember for as long as I stay in footy," Eels coach Dean Widders said.
Both of the Eels' captains, Taufa and centre Tiana Penitani appear in doubt for next week's semi-finals with leg injuries, however.
"We'll have some assessment to do on everyone this week," Widders said.
"There are some tough injuries there. It's getting to that point in the season."
Broncos coach Kelvin Wright said Brisbane failed to meet the standards of their NRLW rivals this year as he lamented their poor discipline on Sunday.
"I thought today we just put ourselves under too much pressure right from the start of the game with the errors that we were giving up," he said.
Up 14-6 at halftime, Parramatta could not turn pressure into points early in the second half and threatened to slip out of the contest when Ali Brigginshaw masterminded a Broncos comeback.
But Taufa burst over to restore the Eels' lead with nine minutes to play, before partner-in-crime Cherrington sealed the result on the right.
The victory helped the Eels exorcise their demons from last year, when a last-round loss to the Broncos ruled them out of the play-offs.
With a victory of 15 or more points, the Titans could have ousted the Eels from fourth but were left to rue a slow start that had them down 12-0 after 14 minutes.
Gold Coast took it up to the reigning premiers in the second half, the sides scoring two tries apiece, but the Titans were unable to close the gap and will finish the season on the bottom of the ladder.
Roosters captain Isabelle Kelly said her side's best was yet to come.
"Every week we're getting better so we just need to stay humble within that and take the victories as they come," she said.
In the final game of the regular season, Newcastle defeated St George Illawarra 30-8 to take a mental edge into next week's semi-final between the two sides.
The Knights and Dragons went blow for blow before Newcastle winger Jessica Gentle slid over on debut, the beneficiary of a Jesse Southwell cut-out pass just before the break.
Newcastle tightened their control of possession in the second half, holding their opponents scoreless and extending their slim advantage into a decisive victory.
"We probably just didn't aim up defensively," Dragons coach Jamie Soward said.
"But in saying that, the club has reached another semi-final.
"I'm really proud of that."
The win continued a stunning turnaround for the Knights, who failed to win a game in their first campaign but finished their second as runners-up in the minor premiership.