Any way you can no till it?  Oregon is a whole different world from ND, but notill here has been a miracle for our clay soils.  25 or so years ago we thought notill was just for sandy ground and it would never work here, but it has been the best thing on that heavy ground.  If you have to use tillage, I can't help other than to say that in the spring don't work it too wet.  Clay is especially unforgiving worked too wet in the spring, unless you have the type of loamy clay where the clods crumble when they dry out.  We have some of that and it is good soil, but the stuff where the clods dry into bricks is nasty, rain doesn't help, only winter freeze-thaw breaks them down.