Bagging another three goals, Mitchell Howlett guided Busselton to a 38-point win over Harvey-Brunswick-Leschenault on Saturday afternoon.
Travelling to Brunswick Oval, the Magpies were forced to contend with the reigning premiers, a strong HBL home crowd, and stormy conditions.
The visitors quickly adapted to the situation, before kicking two unanswered goals and claiming an 11-point quarter-time lead.
Busselton scored another three majors in the second term, and went on to clinch a 5.4 (34) to 0.5 (5) lead at the main break.
Inspired by the words of coach John Baggetta, the Lions regained momentum and posted two goals in the third quarter.
Booting three goals to one in the final term, the Magpies cruised to a commanding 9.7 (61) to 3.5 (23) away victory.
Brent Snook posted two majors, while teammates Jaxon East, Ethan Maguire, Kester Decke, and Jon Meadmore kicked one goal each.
The Collie Eagles moved through to the semi-finals with a come-from-behind win over the Eaton Boomers on Sunday.
Overcoming strong winds and fierce opposition, the Boomers notched up two goals to one in the opening term.
The Eagles recovered to kick two goals in the second quarter, before securing a two-point lead at half time.
Feeling refreshed, the Boomers regained composure and booted three unanswered goals in the third term.
Trailing by 16 at the final change, the Eagles turned it around by scoring a remarkable seven goals to two in the fourth quarter.
Star forward Joel Houghton kicked four goals in the Eagles' resounding 10.12 (72) to 8.11 (59) win at home.
Playing well under pressure, Heath Ryder and Gregory Humphries top-scored for the Boomers with two goals apiece.
Reigning premiers South Bunbury breezed past the Harvey Bulls, 4.10 (34) to 0.4 (4), in week one of the Women's finals series.
The in-form Bethany Bond lined up to kick three of the Tigers' four majors.
Busselton knocked past champions Bunbury out of this year's competition a thrilling 2.4 (16) to 1.6 (12) result.
Round two will see Bunbury face off against Busselton at Payne Park and HBL clash with Collie at Brunswick Oval.