Donaldson opened the scoring with his fourth goal of the season midway through the first half before Taylor, on loan from Sheffield Wednesday, headed in a second after 68 minutes.
City were unbeaten at Sixfields prior to the Bees arriving and they started the game the stronger team. But when Leon Clarke wasted a good chance in the 21st minute, Brentford raced straight up the other end and scored.
A lofted ball over the top got held up in strong wind and Cyrus Christie missed his kick when trying to clear, gifting Donaldson an unopposed run on goal and he applied a cool finish.
Donaldson almost doubled the Bees' lead moments before half-time but Joe Murphy saved well.
Coventry could not clear their lines from Sam Saunders's in-swinging corner and when he flung in another cross Taylor was there to head in from close range - his second goal in three outings since arriving from the Owls.
Farid El Alagui would have made it 3-0 late on but for an alert goalline clearance from Christie.