Liddell, a summer signing from a Championship side Sheffield United, was the forefront of Oldham's attack as they cruised into a 3-0 lead before almost throwing their good work away.
And it was just the paint off the woodwork that stopped Swindon earning an undeserved point in injury time.
Oldham started brightly and went into an early lead following a Liddell corner. His inswinger found Rob Scott unmarked at the back post and he made no mistake with a right side-footed effort.
Seven minutes before half time Liddell stunned the home crowd with a 25-yard pile driver which sailed past keeper Rhys Evans to double his side's advantage.
And it almost got worse for the home side two minutes later when midfielder Richie Wellens tried his luck from range only for the ball to hit the top of the net.
Oldham started the second half as they ended the first and soon added a third when Jerel Ifil's clumsy challenge on Chris Porter gave the referee no choice but to point to the spot.
Veteran striker Liddell stepped up to convert the spot kick to score his third goal in four games.
Swindon came to life in the last 15 minutes after boss Andy King made a triple substitution.
Welsh striker Christian Roberts found space in the box on 79 minutes to fire a low shot past keeper Chris Day to reduce the arrears.
Just five minutes later Swindon gave themselves more hope when Jamie Cureton found strike partner Tony Thorpe in the box and he made no mistake from six yards to set up a dramatic finish.
Swindon went close to earning an undeserved point when Roberts headed wide from substitute Nicky Nicolau's cross before a flurry of Swindon corners.
Jack Smith's first set piece saw Cureton head just wide before Nicolau's corner from the other side saw the former QPR striker's header come back off the woodwork as Oldham held on.