Though it wasn't an official side session, it marked the first time Beckett had been on the mound since May 18 at Yankee Stadium.
The hope is that Beckett will have a full side session before Friday's game at Fenway Park against the Kansas City Royals.
"That's not etched in stone, but I think that's what we're shooting for," manager Terry Francona said.
The earliest Beckett is eligible to pitch for the Red Sox is on June 3 against the Oakland Athletics. Francona isn't sure yet if that date is realistic.
"You know what, I don't know," Francona said. "[Pitching coach John Farrell] and I sat down and talked to him for a little while today, and I think the biggest thing we talked to him about is, 'Don't worry about the date. When you're ready to pitch and pitch effectively, that's what we're shooting for.'
"I think sometimes guys like Beckett, because they care, because they're conscientious, because they want to carry their load, they want to do things too quick. So we really wanted to hit home, 'Hey, just get yourself feeling good and we'll get this figured out together.' And I think he probably understands that. It's just, sometimes he needs to hear it."
How is Beckett feeling?
"I think better, and that's the whole idea," Francona said. "I think every day he feels better, and again, that's what we're trying to do."
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.