The company believes this to be the largest production milestone in Australia's history.
It says it has been achieved through "dedication, commitment to safety and setting in place effective systems to consistently meet 100 operating hours per week of the longwall mine".
Ensuring equipment reliability has also been critical to the consistent production milestones of up to 250 kilotonne a week.
This enabled the longwall team to do their jobs effectively and with faith that systems were in place to ensure the equipment was 100% reliable, according to Anglo American head of underground operations Glen Britton.
He said the achievement is a testament to the commitment and calibre of the team at Grasstree.
“This is a world-class operating team and results like this start with the vision and belief that we can achieve something no one else has done before,” he said.
“From there, we were able to set out a plan for key improvements at Grasstree, starting with improved operational discipline, which demanded clear communication and planning.
“It has been a consistent effort, every shift, every day over the past 12 months with teamwork and safety at the core”
Earlier this year, Grasstree produced 1,200,537 ROM tonnes in one month, beating the previous monthly record set by Oaky Creek North in 2009 by 8000t.
In spite of the current difficult market conditions and the pressures which come with this environment, Grasstree mine has put their best foot forward to deliver this achievement and a new bench-mark for Australian underground coal operations, according to Britton.