Reading striker Simon Church, who opted for a loan move to Huddersfield instead of Barnsley on Friday, laid on the winner for Beckford, who headed home the Wales international's pin-point cross in the 36th minute.
Church twice went close himself as Huddersfield climbed back into the top six with a fourth away win in the Championship this season, while a fourth straight defeat for Barnsley leaves them two points above the drop zone.
The first real chance fell to Harewood, who headed a corner from Jacob Mellis just wide in the 15th minute and the former Nottingham Forest striker fired in a 25-yard shot that was comfortably gathered by Huddersfield goalkeeper Alex Smithies.
Prompted by midfielder Stephen Dawson, Barnsley enjoyed the better possession midway through the first half, but it was Huddersfield who broke the deadlock nine minutes before half-time.
Church found space out wide on the left and sent over a fine cross for Beckford, back in the side following a hamstring injury, to head home into the top corner from six yards.
Barnsley's response was immediate though. Tomasz Cywka arrowed a shot from the left edge of the penalty area just over the crossbar and Dawson's effort from similar distance was well saved by Smithies.
Beckford was replaced by Danny Ward on the hour mark and the visitors then went close to increasing their lead twice in as many minutes.
Striker Lee Novak's shot from the edge of the area was held by Steele before midfielder Keith Southern headed Ward's corner inches wide in the 62nd minute.
Tykes boss Keith Hill sent on former Egypt international Mido for Etuhu soon after, but Huddersfield went close again from another Ward corner, this time defender Joel Lynch heading the wrong side of the post.
Hill sent on teenager Reuben Noble-Lazarus and Jim O'Brien for Cwyka and Dawson respectively and the former made an instant impression when he fired a shot over the crossbar.
Church, a constant thorn in Barnsley's side, forced a smart save from Steele with a 77th-minute shot from inside the box, while the Tykes spurned two golden chances to level in the closing stages but Harewood and then O'Brien both pulled shots wide.