The visitors deservedly took the lead in the first-half as Arsenal's defence was all over the place but goals from Oxlade-Chamberlain and Benayoun made sure Gunners survive
The game came off the back of a disappointing 4-3 defeat at Blackburn at the weekend and recent losses to Liverpool and Manchester United as the pressure has piled on boss Arsene Wenger.
The reserve side Wenger fielded included experienced players such as Yossi Benayoun, Marouane Chamakh and Johan Djourou but they were outclassed for most of the first-half by a team three leagues below them.
The hosts started the stronger of the two and Moroccan striker Chamakh forced Shrews goalkeeper Benjamin Smith to make two fine saves inside the first five minutes.
But it was the visitors who came closest to opening the scoring. Arsenal’s defence was cut to ribbons before Mark Wright hit the post with a shot that crept across the host’s goalmouth.
This should have been a wake-up call for Wenger’s side but they fell asleep again and no sooner had the ball hit the post then James Collins’ attempt was saved by goalkeeper Lukas Fabianski.
Shrewsbury deservedly got their noses in front minutes later, Collins headed in from inside the six-yard box after the home side’s defence went AWOL once more. Johan Djourou got caught on his blind side, Carl Jenkinson didn’t track Collins’ run allowing an easy header past Fabianski following Marvin Morgan’s cross into the box.
The League Two outfit started to dominant proceedings through the ever-threatening Lionel Ainsworth and Mark Wright and were looking like scoring on every attack.
But it was Arsenal who equalised almost against the run-of-play just after the half-hour mark through right-back Keiran Gibbs’ header. Carl Jenkinson’s cross was inadvertently flicked-on by a Shrews defender into the path of Gibbs and his header was just too powerful for Smith, who did get a hand to it but couldn’t keep it out.
The home side started the second-half as they started the first, on top and forcing fine saves from Benjamin Smith.
Joe Jacobson contained Arsenal midfielder Alex-Oxlade Chamberlain as he was baring down on goal as the hosts started to take control of the game and they started to leave one defender back as they looked for the winner.
And it was Oxlade-Chamberlain - on his full Arsenal debut - who got the Gunners in front on the hour mark, his shot squirmed under an otherwise brilliant Smith following an assist from Yossi Benyaoun.
Benayoun then added a third 12 minutes from time as they completed the turnaround after great work from substitute Oguzhan Ozyakup who had only been on the pitch a minute but the score-line in the end flattered the Gunners.