My girlfriend is working for the same company I am, and we want to put our son on both our health insurance policies as primary and secondary. Can you use the same healthcare provider as primary and secondary insurances?

Normally not, and you do realise the very limited amount that is paid though a secondary.

Each company will have its own rules and guidelines and with company policies often they have some of their own specific rules, You will have to contact that carrier

My girlfriend is working for the same company I am, and we want to put our son on both our health insurance policies as primary and secondary. Can you use the same healthcare provider as primary and secondary insurances?

Sometimes yes, in your case, you both hold separate and different policies, so it would be plausible. If I knew the insurance company, which you are referring to, then I could give you a definite yes, or no. Also, you could call the insurance company, and directly ask them, then that would leave no room for guessing.