Rob Herring scored first for Ulster but they ended up losing ground in the race for the play-offs away to conference a leaders Glasgow Warriors.
Ulster were 7-0 up but conceded 30 points without reply to fall to their sixth Pro14 defeat of the season.
The visitors trailed by 20-7 after playing against the strong breeze in the first half at Scotstoun.
Dan McFarland’s side started well but ended the half poorly and their hosts capitalised, finishing off their third try before the interval.
Ulster suffered a 21-18 defeat in their Champions Cup quarter-final against Leinster last Saturday, but looked like they’d put that pain behind them by scoring after just eight minutes here.
Luke Marshall made the initial break down the right wing, before Rob Lyttle almost scored in the right corner.
Ulster remained patient, Billy Burns kicked to the corner and after Kieran Treadwell claimed the line-out, Herring spun off the back of the maul and scored.
John Cooney added the conversion, but with Ulster’s poor set-piece, Glas- gow put pressure on the scrum and line-out and built a platform.
They were level by the 15th minute, and it was similar to Herring’s effort up the other end.
Jonny Gray caught Fraser Brown’s line-out throw, before hooker Brown emerged at the back to score.
Adam Hastings nailed the conversion and followed up with a try four minutes later. Hastings began that move and received the pass from half-back partner Ali Price to score.
He missed the conversion but added a long-range penalty to give Glasgow a 15-7 lead by the 27th minute.
Ulster had a chance to hit back before half-time but Cooney knocked on at the base of their ruck under the Glasgow posts and the danger was cleared.
It was the worst possible ending to the half when a relentless Glasgow attack finished with Stuart Hogg creating the opportunity for former Ulster man Tommy Seymour to score the crucial third try.
Glasgow were 13 points clear at the interval and Zander Fagerson scored the bonus point try in the 44th minute.
Shortly after that, Marshall looked set to score for Ulster but when he was across the try-line he failed to touch it down on time, and, just like Jacob Stockdale last week, he fumbled it forwards.
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