How can I use a router on thick stock (3';) and not get tearout?

I can cut one side of a three inch thick arch with a router, but when I flip the work to its opposite side, I am cutting against the grain. Any ideas?How can I use a router on thick stock (3';) and not get tearout?
Yes.... However you should not make a cut over 1/2 inch (or the thickness of the bit) at 1 pass.The less you ';take off'; the smoother the cut.