"opposing groups" is correct and usable in written English.
For example, "The two opposing groups had little in common and were unable to agree on a solution."
He doesn't tell opposing groups what they have to do.
While we are discussing types, Pink often uses opposing groups when presenting his arguments.
They persuaded leaders of opposing groups to agree with this proposal.
Is it possible that our democracy has been hijacked by two opposing groups, simultaneously?
The opposing groups have almost identical names, which challenge outsiders to break the code.
Today, the opposing groups filed another appeal with the Interior Department.
An opposing group, including Aaron Burr, absorbed the Well Meaners and became the Cliosophic Society.
"You feel it's a fait accompli," said Carol Linn, 61, one of the principals behind the opposing group.
"It could be an organized crime group who was looking for an opposing group," said Alejandro Garza, the top prosecutor in the state of Nuevo León.
Dr. Fallon, of the opposing group of doctors, cautioned that "no firm conclusions could be draw from the Yale study because of the limitations of the design".
The opposing group included the former Chrysler Corporation vice-chairman Robert A. Lutz and the Cow Creek tribe of Native Americans from Oregon, which provided the financing from casino earnings.
