96 Cavalier with check oil light on?

I have a 96 Cavalier; 187, 392 miles; 2.2L...while driving it today, the check oil light came on. I immediately pulled into a gas station and put a quart of oil in it. I started it up, and the light didnt come on for the rest of the ride. When I started it again, the light was back on...I decided that I would get an oil change, even though it wasnt due for about a week. While driving home the light never came on. Then when I went back out later, the light was back on. Any ideas of what this could be? The engine is quiet, no knocking or anything. The cars temp guage is normal...everything appears to be running ok, but I know nothing about cars...