Aberdeen opened the scoring at Pittodrie through Adam Rooney in the 12th minute, the striker taking advantage of a fumble by County goalkeeper Antonio Reguero for his 11th league goal of the season.
Rooney then turned provider in setting up Peter Pawlett for Aberdeen's second five minutes after the break.
Shaleum Logan and David Goodwillie added further strikes to round off a comprehensive win for Aberdeen, who got back on track after an eight-game winning run had been snapped by consecutive draws.
By contrast, County are six points adrift at the bottom, without a win in 11 games.
Elsewhere Kilmarnock, under the interim management of Gary Locke following Allan Johnston's resignation, drew 0-0 at Hamilton Academical.
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