One of Canada's elite business law firms, McCarthy Tétrault LLP, is undergoing a wide-ranging transformation, shedding hundreds of support staff, adopting egalitarian open-plan workplaces with a Starbucks feel, jettisoning fancy corner offices for senior partners and moving away from the traditional practice of billing by the hour.

Overseeing all the re-engineering, radical by the Canadian legal industry's ossified standards, is a non-lawyer: the firm's chief operating officer, Tracie Crook.

"I didn't have a bunch of resistance," Ms. Crook said. "They were ready for change …They didn't know exactly what transformation meant, they just knew that the legal industry was changing."

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Raised in Grand Blanc, Mich., Ms. Crook, 50, joined McCarthy Tétrault in 2011 as a business-world veteran, having previously served as president and chief executive officer of ResMor Trust Co. and as director of the business management office for the TSX Group. Other major Canadian law firms have also brought in non-lawyers into senior roles, as the profession seeks to bring modern business practices into the still often fusty legal world. The moves have come as the sector grapples with new competition from global players and changing demands from clients, who want more efficient services and more predictable bills.

Over the past four years, McCarthys, which has about 500 lawyers across Canada and an office in London, has reduced its support staff by about 200 people, mostly by slashing the number of legal assistants. Previously, each partner had one to themselves.

Now, there is one legal assistant for almost every four lawyers, and some of the assistants' old duties, such as preparing documents and handling billing, have been centralized.

The firm's physical space is changing, too. After seeing some new open-concept layouts at law firms in Australia, McCarthy Tétrault CEO Marc-André Blanchard sent Ms. Crook there to see how they worked. She ended up hiring an Australian architect to bring the new ideas here, starting with the firm's Quebec City and Vancouver offices.

Partners' offices are now in the middle, with glass walls, and everyone has the same size – 10 feet by 10 feet – and the same desk. The rest of the space is open concept. Lawyers move around and work in groups, carrying laptops and staying connected with headsets. There are greenery and TV screens in common areas, and few walls for the expensive art that still hangs at many other high-end law firms, including at McCarthy Tétrault's own still unremodelled Toronto headquarters.

Before the open-concept designs were made for Quebec and Vancouver, McCarthys staff were consulted, Ms. Crook said: "We tried to hear everything that they wanted. They wanted more of a Starbucks atmosphere so they could take their computers and work there."

Even the staircases have been constructed to be slightly narrower, in an effort to encourage work colleagues to interact. Mr. Blanchard says the floorplan is encouraging more collaboration and mentoring between younger associates and the firm's senior partners.

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"What first started as a way to reduce our real estate footprint became a powerful tool to enhance collaboration and teamwork throughout our offices and the firm," Mr. Blanchard said.

But it is also saving money. McCarthys, both because of its office layout and its rationalization of support staff, has saved on one of its biggest expenses: real estate. It has subleased one of its nine floors near the top of Toronto's TD Bank Tower, and has reduced its footprint in Quebec and Vancouver. Its Montreal office is next.

Ms. Crook has also overseen changes to how McCarthys deals with its clients, and the firm's "project management" system. Now, the firm has what it calls a "client service innovation team," which reports to Ms. Crook, and which is made up of half lawyers and half non-lawyers. The team works with the lawyers on a file to figure out new ways to bill for legal services that suit a particular client, such as offering a fixed fee instead of just totalling up billable hours. Or the team might suggest outsourcing some of the work.

It's a kind of change being looked at by law firms in Canada and elsewhere – even though many of the ideas are commonplace in the outside business world, and already adopted by other professional firms, such as accountancy firms.

Even Ms. Crook says she was taken aback by how outdated law firms were when she took her current job.

"When I walked in here, I was a little bit surprised," Ms. Crook said. "But I think that's been the fun part of it, to actually know what needs to get done … And at McCarthys, what's been amazing is how accepting they've been."