Ayr United 4-1 East Fife
Craig Malcolm fired a hat-trick to secure Ayr United's play-off place by thumping an East Fife side who at least avoided outright relegation.
Arbroath drop to League Two after their defeat by Airdrieonians, while the Fifers face the League Two play-offs.
Liam Buchanan's headed consolation goal for them came eight minutes from time.
Brian Gilmour scored the other goal for an Ayr side who have been in the top four in League One all season and remain in the hunt for promotion.
After Craig Johnstone had hit the bar for the visitors early on, Ayr took the lead three minutes before the break when Malcolm's lobbed finish gave them a half-time lead.
The striker picked up where he left off after the break, with two-close range finishes completing his hat-trick.
Ayr now host Cowdenbeath in the first leg of their Championship play-off semi-final on Wednesday.
Meanwhile, East Fife travel to Cumbernauld to face Clyde, who finished fourth in League Two, in their League One play-off semi-final first leg.