Tesco managers are promising customers shorter checkout queues at their store in Cowley Road following a revamp.
Last month, customers of Tesco Metro were asked to be patient while major works were carried out inside the store.
Managers say extra staff are now being recruited to work at the checkouts.
The shop is undergoing a "refresh" - meaning shoppers have to move around scaffolding to pick up their groceries.
Justin Walden, 33, of Hurst Street, East Oxford, became so frustrated he took photos inside the store showing queues building up at the tills.
After visiting the store at 3.30pm, he said: "I was in the queue for 40 minutes. I can't understand why eight tills were closed.
"Surely Tesco managers are aware of their peak times, so why are there so many tills closed at busy times of day?
"It's not just me I feel sorry for but all the elderly infirm people who find waiting in these queues tiring."
Having visited the store again on Tuesday, Mr Walden added: "The situation has not really improved - the shop is like a bombsite. I feel they should have closed for a week to get the work done.
"The place is always packed with customers and yet half the tills are closed - I'm off to Sainsburys."
Tesco spokesman Juliette Bishop said: "The refresh of our Metro store on Cowley Road is progressing well. The work is quite extensive and we apologise if any customers feel that they haven't received the service normally expected from us.
"The store will be ready for its relaunch next month and along with the improvements, it will benefit from extra staff recruited for the checkouts."
Once work is completed, new features will include a Tesco Direct desk, where products such as furniture and electrical equipment can be ordered and delivered to customers.
The store has also said there will be an increased range of beers, wines and food.
Ms Bishop said the work was due to be completed by April 2.
She added: "We would ask customers to be patient while this work is being carried out.
"It's always difficult to keep a store open and carry out work at the same time but that is our policy when we refresh one of our stores."
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