We asked our shoppers to order the same list of items as in The Grocer 33 this week.
While the majority of our mystery web shoppers found the retailers' systems easy to access and to navigate, when the moment came to choose a delivery slot, only one of the five (WaitroseDeliver) was able to offer our shopper the option of a next-day delivery.
Tesco.com and Sainsbury's.co.uk could not deliver our shoppers' goods for two days after their orders were placed on the morning of Wednesday, 25 October, while the earliest that our Brighton-based Ocado shopper could expect her groceries was three days later. And our online shopper at Asda.com was faced with the most disappointing scenario of all - the earliest that he could expect his goods to arrive was between 6 and 8pm on Saturday, 28 October.
On a more positive note, when it came to punctuality all the deliveries arrived well within their designated time slots -bar Ocado's, which was 40 minutes early when our shopper was out.
All our shoppers described their delivery drivers as helpful and extremely polite, although most said that more effort could have been made in helping to bring bags into the kitchen or at least over the doorstep.
However, these small achievements were soon forgotten when our mystery shoppers set to work unpacking their goods.
None of our online guinea-pigs received a full basket of items exactly ordered and, with the exception of Ocado, all deliveries had at least one substitution, as well as various out of stocks and an array of un-ordered or unwanted items.
Take our Asda.com shopper, for example. As well as two no shows and one substituted item, our Asda.com shopper was also sent an extra un-ordered bottle of Radox Herbal Bath and a jar of Asda's own label classic pesto. No hardship for our shopper, but a waste for Asda.
Worse was our WaitroseDeliver shopper's experience. She received double her ordered amount of chicken breasts - and was charged for them.
The issue of substitutions has been immensely contentious in the past, and while the online retailers have improved in terms of the items they select for substitutions, the sheer number of switches still disappointed our mystery shoppers.
Sainsbury's.co.uk failed to repeat the impressive improvement seen in the last of our quarterly surveys and once again totted up the largest number of substitutions at four, followed by WaitroseDeliver with three, Tesco.com with two and Asda.com with one.
While all the switches were acceptable, in the vast majority of cases the substituted items were a good deal pricier than the original products ordered - and our Tesco.com and Sainsbury's.co.uk shoppers were charged the higher prices of their substituted items.
In fact, our Sainsbury's.co.uk shopper only found out about the price difference two days later because her receipt and pricing paperwork had "not been ready" when the driver came a'knocking.
Meanwhile, packing - in particular the number of plastic bags used to convey orders - was another contentious issue for our mystery web shoppers.
While there was no sign of the brown paper bags that Ocado has been trialling as part of a drive to boost its eco-friendly credentials, the online retailer managed to use just seven bags to deliver our shopper's goods.
Our Tesco.com shopper went one better at six.
However, the remaining three online stores did not appear quite so green-fingered.
Staff at WaitroseDeliver's base had packed our shopper's goods into ten plastic bags and Asda.com used 12.
However, the worst offender - using a whopping 14 plastic bags to deliver just 33 items - was Sainsbury's.co.uk.