Carchiba- I've gone from Eugene to Redmond (north of Bend) on OR 126, so I can offer some advice.
Unless you are a particularly strong rider, I would recommend breaking it into at least two days, if not more. The most direct route between the two using 126/242/20 is about 120 miles (195km) and crosses McKenzie Pass, elevation elev. 5335 ft/1623 m. From Eugene which is near sea level, there is a lot of climbing to do to get to the pass, and parts of the climb are steep. You could instead cross the Cascades at Santiam Pass which is lower at 4817ft /1468 m but is longer (126/20) at 130mi/210km.
Traffic can be heavier on 126 closer to Eugene, but after McKenzie Bridge it drops off. Santiam Pass is busier than McKenzie. Shoulder conditions vary.