They're supposed to go to seed when they are planted at the wrong time in the wrong season. They will probably not produce any sprouts. The good news is that you can replant now and maybe even in July depending on what part of Oregon you are in.

You want to plant them to time them for a fall/winter crop.

Check with your state's Extension Service. Each county should have it's own Cooperative Extension Office which provides free publications and information for the asking. They will have valuable vegetable/gardening tables available specifically for your area determined by universities and horticultural research scientists who have collected data from growing those crops in your state. Your tax dollars are already paying for this service so you may as well get some use out of it.

Vegetable Planting and Planning Calendar for Missouri (download the pdf) complete with spring and fall planting dates (underneath the spring planting dates for appropriate crops), how much to plant per person, etc. They can also tell you the average last frost date for your area and ideal planting times for specific crops and varieties in your area.

See how detailed this example is:

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Here is a link that might be useful: Oregon Planting Dates for Vegetables

Well I planted Brussels sprouts this last winter, it withstood frosts well, began to form little sprouts and I was really looking forward to eating them. The minute it started to warm up in early spring (and I'm talking barely warm, not hot) it formed a flower stalk on top, then the sprouts started loosening up and burst into flower themselves. So much for Brussels Sprouts. I think that in my case it happened because the winter was unusually cold, and when early spring came the change in temp triggered the flowering. I'm going to try again this fall to see if that makes a difference.

Thanks guys. I think that's exactly the problem them - I don't think I nessarily planted them at the wrong time based on our NORMAL weather here, but this year wasn't normal - 90s in May. I will pull them out and start over. I suspect that will work fine, since it doesn't freeze here most years until well into the December most years, so I've still got plenty of time for cool weather crops.
Stacey

Oh, and I'm in the Willamette Valley (or more accurately about 1000 feet above it in the hills). i can never remember what zone I am, but its very, very mild. So I can grow great fall/spring season crops - I actually have lettuce coming up wild in the middle of my yard, but have lots of trouble with anything that needs heat - no melons for me, and I'm lucky if I get one eggplant to a plant.
Stacey