The AIM-listed firm said Whittle has agreed to continue working with the company to ensure a managed handover, adding that his contract termination date will be October 15 unless otherwise mutually agreed.
Quadrise said its executive chairman Mike Kirk and its chief executive Jason Miles will continue to lead the management and that its existing resourcing will allow it to continue to advance its portfolio of project opportunities in line with their current schedules in the short term.
The group added that it will commence the search for a replacement COO immediately and that further announcements will be made as appropriate.
"We thank Mark for the key role he has played in the development of Quadrise and wish him well in his new role. Jason and I will continue to lead the business to ensure that we deliver the projects as planned. We do not expect any changes to our project timetables as a result of Mark's departure", Kirk said in a statement.
Shares in Quadrise were 1.8% higher at 3.4p in late afternoon trading on Friday.