After scoring twice in the win at Bradford, Beckett went one better and extended Oldham's impressive run of form which has put them in the heart of the promotion battle.
Blackpool are still in trouble near the foot of League One and paid a heavy price for their careless defending. They were slammed as kamikaze by angry boss Simon Grayson but Oldham cashed in with a great come back from 1-0 down.
Blackpool almost grabbed a surprising lead through Marc Joseph, but Oldham gained the upper hand as Beckett and his strike partner Paul Warne linked up well.
Warne was denied by keeper Lee Jones before Beckett headed wide from a cross by wing-back Chris Taylor.
Beckett was off target again and Blackpool sounded a warning when home goalkeeper Lee Grant made a good save from Keigan Parker.
The visitors eventually broke through on 42 minutes when Keith Southern controlled a loose ball 12 yards out and drove it into the roof of the net.
Oldham replied before half time as Taylor's cross from the right found Beckett inside the six-yard box and he came through a crowd of players to find the net.
Blackpool continued to Beckett too much space and, after he almost scored a second on 51 minutes, he did make it 2-1 with a simple close range finish from Warne's header four minutes later.
Blackpool pushed forward and nearly equalised when midfield man David Fox hit a pile driver from at least 25 yards which keeper Grant performed heroics to tip over the bar.
A free-kick by Parker grazed the woodwork on its way over before Blackpool were finished off by a penalty in the 86th minute. Marcus Bean handled a header by Mark Hughes and Beckett stepped up to send Jones the wrong way for his 14th goal of the season.