Several caravans were seen occupying the car park in Station Road on Thursday, the day after the chain shut its store before moving to its new site in Shrewsbury Road.
Shropshire Council served notices to the group, who had left the site by Saturday evening.
Councillor Steve Charmley tweeted: "Great work by @ShropCouncil to clear The former Oswestry Morrisons site of its unwanted visitors, thanks to the clean up team for doing such a great job. @ShropshireStar @advertizer #jobwelldone"
The will be now secured to prevent it happening again.
Earlier, Councillor Charmley said: "There are a lot of caravans and vans. As a council we've gone through the normal processes to move them on.
"Normally you find that the travellers know the law better than anyone, so they know how long they've got before they need to move on.
"It's not the most aesthetically pleasing thing to have in the town centre, but they're self-contained in a walled car park. They're not sprawled out and causing a lot of disruption."
He added: "I'd advise anyone with car parks or land to be aware. We don't want another repeat of this in the town."