Ballymena-based O'Kane Poultry is to pay workers more than £200,000 after withdrawing overtime payments without proper consultation.
The move in April 2009 meant all overtime was cancelled except for July 12 and Christmas Day.
Workers had previously been paid double time on Sundays and public holidays and time and a half on Saturdays.
A union challenged the move and won compensation for employees.
The Bakers, Food and Allied Workers Union (BFAWU) had argued the changes were unfair, and after attempts to resolve the matter internally came to nothing, the union brought in law firm, Thompsons McClure.
The firm secured a settlement of £23,566 to be shared between the union's 44 members and an additional £150 each for another 1,280 employees.
O'Kane employee and BFAWU representative Jim Neill said the employees had fought to stand up for their rights.
He said that employees were given only a few days notice of the changes to terms and conditions and 520 workers had complained.
He added: "As an employee you can complain but without the muscle of the trade union behind us I think our complaints would have gone unheard.
"With the union's backing our employer has had to treat us with respect."
Billie Gallagher, a full-time official with the BFAWU said the outcome showed unions making "a real and tangible difference to workers' lives".
"An employer who thought they could ride roughshod over their employees expecting they would sit back and accept detrimental change being imposed on them has been brought to account.
"We have ended up with a sizeable sum for our members and a positive result for non union members as well who will benefit from our intervention."
George Kilpatrick from Thompsons McClure criticised the company's failure to resolve the dispute internally.
"They mistakenly thought the BFAWU was going to take all of this lying down," he said.
"We are pleased that through a combination of litigation and negotiation we have secured a positive result for union members.
"In future, O'Kane would be better to engage in constructive discussion and negotiation with the union to avoid litigation."
O'Kane's was recently acquired by Brazilian-owned company Moy Park.
Managing Director of O'Kane Poultry, Tony O'Neill, said the firm had undertaken an "extensive consultation process" with the trade unions prior to the introduction of the "changes in working practices".
He said "global competitive pressures" at the time meant if it "had not made these changes, all jobs at O'Kane's would have been at risk".
"The changes in working practices were implemented after this consultation process," he added.
"Following their introduction we received a number of grievances which were dealt with internally.
"The unions also began to proceed with a number of industrial tribunal claims.
"At this stage we approached the Labour Relations Agency in an effort to achieve the best outcome for all our employees and for the company as a whole.
"The result of this mediation process is that all our employees have received compensation, and we are satisfied with this outcome."