Hooker Johnny Matthews scored a hat-trick of tries as Glasgow Warriors recovered from an early blow to thrash bottom side Zebre.

But three tries from Matthews and one from JP du Preez put Glasgow in control by half-time at Scotstoun.

Stafford McDowall, Josh McKay, Thomas Gordon and Fraser Brown all went over after the break.

Glasgow move up to third ahead of Ulster and two clear of fifth-placed Munster, who held off visiting Scarlets' comeback, as Zebre continue their wait for a first URC win of the season.

The home side had that precious bonus point in the bag by the break, but if their 24 first-half points suggested a free-flowing machine, the reality was a touch different. Despite the scoreline, they played within themselves for much of it.

They fell behind when Zebre started with an edge that took their hosts by surprise. The Italian forwards created the platform and Cook took advantage from close-range, tapping and scoring while Glasgow snoozed.

It was sloppy, pedestrian, uneasy on the eye. You always knew that Glasgow were going to get on top of things, but they made heavy weather of it in the beginning.

Where they had joy - buckets of it - was through their line-out. Every score they mustered came out of touch. Zebre had a resigned air anytime they shaped up close to their own line.

Matthews got his first after 10 minutes. A huge drive, an opposing pack bullied, a touch down and conversion from George Horne. Jacopa Trulla put Zebre back in front with a penalty, but the Matthews show carried on after that.

Penalty to touch, haunted look on Zebre faces, maul, try. Last April, Matthews scored a hat-trick against Zebre and there was an absolute inevitability about him repeating the feat here.

He did, but not before providing an assist to Du Preez for Glasgow's third score. The damage was done off a Zebre line-out this time. Scott Cummings got up to mess with their ball, it went loose on the floor, Matthews gobbled it up and fed his lock.

Not long after, the hooker's groundhog night continued. Penalty, touch, rumble, score. Horne added the conversion and, without having found any tempo or making a single line break or creating much in the way of cohesive rugby, Glasgow led 24-8. For Zebre, it was death by line-out.

Playing for Zebre is a tough old station. As a team, they've shipped an average of 37 points per game in the URC and Glasgow didn't take long in the new half to inch towards that number. Remarkably, it wasn't from a line-out.

Cummings charged down a clearance kick, Rory Darge scooped up the loose ball, gave it to Horne, who ran away and put McDowall over. With the extra two, Glasgow's lead had stretched out to 31-8.

When it rains, it pours. Glasgow were like a cat with a mouse. Marco Manfredi, the replacement Zebre hooker, was binned, a sacrificial lamb amid a rocketing penalty count.

Glasgow had a scrum in the Zebre 22, threw some deception into the mix moving right, found Weir, whose wide pass beat the Zebre defence and gave McKay a straightforward run-in.

Horne put over another conversion and the gap was 30. Glasgow, you felt, were still no higher than third gear.

Franco Smith sprung his bench and brought on some of the likely lads for Scotland against Ireland next Sunday. On came Fraser Brown for the prolific Matthews and in came Jamie Bhatti too.

Stade de France, it was not. Next time we'll see them will be Murrayfield on Sunday week. Different rugby planet, that.

Glasgow were not yet done. A lovely strike play and Gordon was under the posts and that score brought it to 45 points. Brown's late blast from a few metres - a fourth try from a Glasgow hooker on the night - took it over the half century.

They still have work to do in their three remaining games - Munster in Limerick are up next on the 24th of the month and what a game that promises to be.

However, that top-four spot, and home quarter-final that goes with it, is well within their reach now.

Glasgow Warriors head coach Franco Smith: "I think we weren't at our best - I think there were a lot of other points to be scored. But they guys stuck in and it was a workmanlike performance.

"Our plan was to outmuscle them and it was not our best performance but an important one."

Glasgow Warriors: Smith, Forbes, McDowall, Johnson, McKay, Jordan, G Horne, Dell, Matthews, Berghan, Bean, Du Preez, Cummings, Darge, Vailanu.

Replacements: F Brown, Bhatti, Kebble, Samuel, G Brown, Gordon, Dobie, Weir.

Zebre: Kriel, Trulla, Boni, Lucchin, Gesi, Eden, Cook, Buonfiglio, Ribaldi, Nocera, Krumov, Zambonin, Andreani, Kvesic, Ruggeri.

Replacements: Manfredi, Rizzoli, Neculai, Uys, Licata, Jelic, Prisciantelli, Mazza.

Referee: Chris Busby (IRFU).