Colts is now one win away from claiming back-to-back Bunbury and Districts Cricket Association premierships, following a decisive victory over Eaton.
Colts opening batsman and wicketkeeper Jaysen Miguel notched up a remarkable 69 runs during his two-and-a-half hours at the crease.
However, with Colts stranded on 4/36 early on, Eaton looked set to claim victory.
Captain Cruize Ciallella responded with 40 off 66 balls (including three fours), before being caught by Cory Fitt.
With assistance from tailenders Blaze Rosinski (19) and Joe Barningham (26 not out), Colts was able to post a whopping 7/208.
Following a phenomenal spell from Colts' bowler Josh Topliss (3/18 from six overs), Eaton was stranded on 4/10.
Despite solid efforts from captain Clint Hewson (28), Clayton Caltsounis (24), and Fitt (21), Eaton was dismissed for 128 after 39.2 overs.
Leschenault knocked Hay Park out of the competition with a three-wicket win.
Redbacks Kris Miller (28, including five fours) and Fraser Thompson (37) upped the run rate, before Jono Whitney made a half-century off 66 balls.
Hay Park posted a respectable 168, following a swift lower order collapse.
Leschenault captain Matt Buchanan knocked 49 (including six fours), before Steven Denison made a resounding 84no.
The Green Caps reached Hay Park's total with 7.4 overs to spare.
Eaton will take on Leschenault this Saturday's preliminary final showdown.