Barry’s two goals were his first in open play this season as Martin O’Neill’s side revived their slim UEFA Cup hopes.
And Agbonlahor scored for the first time in 2008 to condemn the Trotters to their seventh defeat in their last eight matches with sub Marlon Harewood completing the rout.
After nine minutes Villa went in front through Barry’s header after a superb Ashley Young cross.
A quickfire move down the left carved open the Bolton defence with Young finding the overlapping Barry and his cross was deflected past Ali Al Habsi by Agbonlahor (55).
Barry’s goal-bound effort took a deflection off Andy O’Brien before beating Al Habsi to make it 3-0.
And sub Harewood (85) glanced home the fourth.