If you're looking for a meeting place or a good stop around ½ or halfway between Lake Oswego and Sacramento, you can try Ashland, OR, which is about 4½ hours south of Lake Oswego, or about 4½ hours north of Sacramento.
Other possible places to stop near the midpoint include Swiss Bar, Hawkinsville, and Hornbrook.
About ¼ or a fourth of the way, you can stop at Roseburg, OR. This is about 2½ hours south of Lake Oswego.
About ⅓ or a third of the way, you can stop at Civil Bend, OR. This is about 3 hours south of Lake Oswego.
About ⅔ or two thirds of the way, you can stop at Redding, CA. This is a little over 6 hours south of Lake Oswego, or almost 3 hours north of Sacramento.
About ¾ or three fourths of the way, you can stop at Red Bluff, CA. This is almost 7 hours south of Lake Oswego, or a little over 2 hours north of Sacramento.
If you drive straight through without stopping at all, the total distance is 574 miles. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 8 hours, 55 minutes.