Longford Town 1 Drogheda United 2
Guy Bates scored for the third match running as Drogheda moved eight points clear at the top of the table ahead of Shamrock Rovers meeting Bray Wanderers on Tuesday night with a clinical dismissal of bottom side Longford.
Longford started well with the league's topscorer Dave Mooney coming close on two occasion before 20 minutes was up.
The first needed a very good save with his feet from Dan Connor after Mooney worked a one-two with Daire Doyle to get himself clear on goal.
Mooney then drove a fierce shot narrowly wide as Drogheda survived again.
But a terrific goal on 35 minutes brought Drogheda their lead.
Brian Shelley worked a one-two with Eamon Zayed to cross for Bates to sidefoot home.
Paul Keegan added Drogheda's second goal right on half time when stooping to head home Richie Baker's corner.
Longford battled hard throughout the second half and Ian Ryan got their consolation goal in the final minute.