There seems to be a slow growing trend for large companies to offer in-house clinics for employees. Right now just over 20% have them and another five are planning to open them.
Doctors who run these in-house clinics are saving money by not having to pay overhead and staff or to even fill out insurance forms. They in turn pass the savings to the employee who comes and sees them. The companies save money by not having their workers ignore early symptoms and having to go see specialists when illness progresses. The employees also seem to make less visits to the ER. Companies end up saving, in one year, more than twice what they paid to set up the clinic in the first place.
Many employers are reluctant to establish clinics because it can be difficult to see future savings.