A fantastic Stephen McAlorum strike from outside the box 10 minutes from time earned Glentoran a deserved three points at the Oval.
Curtis Allen hit the sidenetting in the first half and fired another gilt-edged opportunity over the bar.
Andy Coleman denied Allen before the break and also saved a McAlorum thunderbolt after the interval.
Willie Garrett and Johnny Addis hit the woodwork but the three points saw the Glens move up to seventh in the table.
Midfielders McAlorum and avid Howland returned to the Glentoran team and both were influential for the dominant home side.
Coleman tipped Allen's effort onto the bar and then Dermot McCaffrey made a fine sliding challenge to deny the dangerous Allen.
The Swifts' best chance fell to Grant Hutchinson but he sliced the ball over the bar when it seemed easier to score.
Garrett rattled the woodwork and Addis hit the bar, before McAlorum eventually opened the scoring in the 80th minute.