This guide is for general information only and is not legal advice. Laws change — verify current rules with your state DOT or a licensed attorney before relying on this for any legal matter. Read full disclaimer.
The rule
Oregon requires lamp on the front emitting a white light visible from a distance of at least 500 feet to the front. For the rear, red reflector or red lighting device on the rear visible from all distances up to 600 feet when directly in front of lawful lower-beam headlamps. The rule applies in darkness or any condition of reduced visibility. See ORS 815.280 (Violation of bicycle equipment requirements).
The cheapest way to stay legal in Oregon is a USB-rechargeable front white light and a rear red light or reflector that meets the spec above. A $30 light set covers it.