The Athlone side were favourites to beat their Roscrea opponents in the Cotter decider after knocking out the holders St Peter's in the semi-final the previous Wednesday night.
Nonetheless, a 4-0 win over Killavilla - who are clearly the third best team in the Senior Division this season behind the big two from Athlone - was not in the script.
Colm Hyland helped himself to two of the goals, Benny Magennis scored once and unfortunate Killavilla also saw their own player Brian Franks net an own goal.
Willow Park had two good reasons for wanting to win the Cotter Cup. Firstly, they knew it would be the first step to a possible quadruple.
And secondly, it was won last year by their arch rivals Peter's, who beat Mullingar Athletic 4-0 in the decider.
Willow boss Tony Sullivan had to field without a key member of his midfield, ex-Galway United and Athlone Town man Colin Fortune, and while they played plenty of attractive football in the early stages of the decider, they were slow to threaten.
When they did, Killavilla defender Brian Brooks - who once again used the match to showcase his extraordinarily long throws - was able to snuff out the danger, especially when Magennis tried to profit from Ronan Frawley's searching ball.
The game was half an hour old when Killavilla finally cracked, the unlucky Franks turning the ball past his own keeper Keith McMahon as he tried to block a Mark McConnell effort.
McMahon then did well to save a shot from Magennis but it was 2-0 before the break when Robbie Shine fed Hyland and he beat the keeper with a super finish.
Willow were comfortable in the second half and Magennis's goal was a peach to the top corner, while Colm Hyland's second arrived when Michael Harney released him from a Gary McHugh cross.
Clonbonny hold nerve to clinch Division 3B crown
CLONBONNY clinched the CCFL Division 3B title with a 1-0 win over Clara Town B last Wednesday night.
Leinster Junior Shield finalists Banagher United, whose game the same evening against Moate Celtic was postponed, were hoping for a favour from Clara but it was not to be and they must now be content with the runners-up spot.
Ian Dunne Memorial kicks-off on June 8
TULLAMORE CCFL Senior Division side CK United are once again hosting a town league this year.
The Ian Dunne Memorial Cup usually attracts numerous players out of the woodwork and this year it will kick off on Tuesday evening, June 8.
The closing date for entries is this Friday, May 28 and it will cost €250 to enter a squad of 20 players.
The matches will take place at CK's ground in Puttaghaun.
For more information, contact Paul O'Meara on 087 9433677.
A REMINDER: the CCFL annual general meeting is on tonight (Monday, May 24) in the Bridge House Hotel, Tullamore at 8.30pm.
And don't forget to book tickets for the league's awards night and annual dinner, also in the Bridge House, on Friday week, June 4.