But the Railwaymen were left sweating in the closing stages after Cheltenham grabbed a late goal against Doncaster.
Fortunately for Steve Holland's side, Bournemouth were unable to replicate that at Carlisle.
When news of the Cherries' 1-1 draw at Brunton Park filtered through, there was widespread relief around Gresty Road after a dreadful afternoon.
It meant that Crewe's result was academic and Bournemouth were relegated in the fourth bottom spot despite their late surge.
Crewe failed to get the point they needed when they went down to Bournemouth a week ago and they never looked like securing safety by their own hand after they fell behind as early as the fifth minute.
A dreadful piece of slack play at the back saw Kenny Lunt gift Deane Smalley a one-on-one with Ben Williams and the youngster fired through the keeper's legs.
Neal Eardley added a second against the nervous home defence when he took Smalley's pass and crashed an angled drive home.
The Wales international midfielder notched his second of the game in even more stunning fashion just before the hour mark.
When his 25-yard right-footer found the top corner, Crewe were effectively out of contention.
Gary McDonald tucked the fourth past the helpless Williams and there were still more than 20 minutes left to play.
The Crewe faithful were left to rely on results going elsewhere, although Steve Jones did manage to grab a late consolation when he fired under substitute keeper Richard O'Donnell.
Crewe coach Steve Holland said: "It was very important that we stayed up but it was a desperately disappointing finish which only highlighted the job that needs to be done to make things better.
"It just needed a point but we ended up losing 4-1. We've played Oldham three times this year and they've beaten us three times.
"They've only finished in mid-table but they've been much better than us all round the pitch."