Anderson, recovering from Tommy John surgery, threw 20 fastballs in the bullpen session.
"It was quick, it was efficient, the command was there," manager Bob Melvin said. "Once he felt a little something, we wanted to take a step back because he was on such a progression, but every time I've seen him throw, he's been terrific. It looks like a guy just throwing a bullpen. Good first start getting back on the mound again."
Anderson encountered forearm stiffness commonly associated with the Tommy John procedure in mid-May. He'll continue throwing bullpens, while upping his pitch count, and is hopeful to make a start in Oakland before season's end.