Directly from Tripcheck.
Oregon Chain Law
Oregon's chain law applies to all highways throughout the state. When you drive in winter conditions, you may see signs telling you to carry chains or traction tires and when you are required to use them. In some areas, lighted message signs also will advise you about chaining up. Traction tires may be used in place of chains on vehicles rated at 10,000 pounds gross vehicle weight or less and that are not towing or being towed.
Studded tires are legal in Oregon from November 1 through March 31. Because of the damage caused by studded tires, the Department of Transportation encourages motorists to use studded tires only when necessary. Delaying putting on studded tires or using other traction tires is helpful to the condition of the highways.
For placement of chains or traction tires go to Minimum Chain Requirements. For information on traction tires go to Traction Tires.