Maybe it is the oil in your skin causing the foundations to oxidize? Or the product you are using under the foundation? (Like too much moisture)
I can't tell you about a good MAC foundation because all the warm colours have been too pink or peach for me, but NARS oilfree and Dior Forever never oxidize on my skin. Laura Mercier's oil free did oxidize, Perscriptives oxidized big time, MUFE are all too pink for me too try, L"Oreals are all too pink as well as Shiseido and Lancome but Revlon's ColorStay was a cheapie that did not change up on me. It takes major road work to find the right foundation for a person.
Make sure you carry blotting papers and use a good translucent powder.