Slick Down edged out their hosts in the curtain-raiser at Brewster Park yesterday.
Peter McGrath's men always looked sharper in front of the posts but did not underline their supremacy until midway through the second half, when corner-forward Jack Haughey slid home the clinching goal.
Fermanagh substitute Tommy McCaffrey gave the hosts a glimmer of hope when he reacted quickly to hit a smashing goal after Eddie Courtney's free came off the post in the 41st minute.
And there were fleeting visions of an upset when Courtney equalised with a mammoth free to make it 0-8 to 1-5. But Haughey's strike made up for two earlier goal chances spurned by Tom Grimley and Haughey himself.
Down wing-back Joe McDermott put them into an early lead after just 20 seconds but this was negated by a pointed free from Courtney. Erne wing-back Paul Coalter then hit the point of the half to put the hosts ahead.
Down were denied the first of three goals when Shane O'Hara stuck out his foot and denied Donal McKeever's effort.
Both sides hit four wides each before McKeever put Down ahead when his shot at goal careered over the bar on 25 minutes.
The second half was played at a faster tempo and Down seemed to be cruising but McCaffrey's goal and Courtney's accuracy kept it close but Down deservedly made the quarter-finals.
SCORERS - Down: J Haughey 1-2, D Doyle 0-2, T Grimley, C McGrady, S McGonigle, J McDermott, D McKeever, D McAleenan, D McKeown 0-1 each. Fermanagh: E Courtney 0-5 (3f), T McCaffrey 1-0, P Coalter 0-2, E McManus 0-1.
Down - R Burns; A McDonald, A Doherty, M O'Hare; D McKeever, R Wells, J McDermott; D Doyle, D McCarthy; C Gallagher, S McGonigle, R McAlinden; J Haughey, T Grimley, C McGrady. Subs: D McAleenan for McGrady, P O'Hagan for McGonigle, D McKeown for Gallagher.
Fermanagh - P Sweeney; S O'Hara, N McMahon, C Corrigan; P Coalter, P Leonard, M Beggan; J Allen, N Shannon; L Jones, E Courtney, C Murphy; C Logan, S Keenan, E McManus. Subs: T McCaffrey for Jones, N Carson for Logan, G McManus for Allen.
Ref - S Hurson (Tyrone).