The phrase "are primarily engaged" is correct and usable in written English.
It can be used to describe the main activities or focus of a person or organization.
Example: "The researchers are primarily engaged in studying the effects of climate change on marine ecosystems."
Alternatives: "are mainly involved" or "are chiefly occupied".
Market makers are primarily engaged in the business of assisting clients in executing their desired transactions and are responsible for providing fair prices.
All these groups except the trader Hausa population are primarily engaged in farming and herding (cattle, goats, sheep), but fishing is also important along the riverbanks.
But the service properly contends that it must ensure that these groups are "primarily" engaged in social welfare, not political campaigning, to merit tax exemption under section 501(c)(4) of the tax code.
But, as the Court of Appeals recognized, this cannot be true of those organizations that are primarily engaged in research, advocacy, or public education and that use their own paid staff to carry out these functions as well as to solicit financial support.
As a result, some people have suggested that we are primarily engaged in proprietary trading.
Meeting this training need places an additional training burden on clinical surgical staff who are primarily engaged in catering to patients' need for these surgical procedures.
And the gluteus maximus, the largest muscle in the human body, is primarily engaged only during running.
At the beginning of the 20th century the people of Mongolia were primarily engaged in the subsistence herding of livestock.
Under current law, tax-exempt 501(c)(4) organizations are supposed to be "primarily" engaged in social welfare work.
But, in enforcing the law, the I.R.S. decided they need only be "primarily" engaged in social welfare, not exclusively.
It was primarily engaged in the production, refining, marketing, and shipping of crude oil and natural gas.
