The stores - located at Wellington in Somerset, Penshore near Worcester and Lancing near Worthing - range in size from 10,185 sq ft to 13,840 sq ft.
The acquisitions mark an apparent u-turn for Asda. Earlier in the year, Andy Bond claimed he had ruled out acquiring any Co-operative Group stores on the grounds that they were too small.
The retailer already has a 8,313 sq ft store in Billingham, in County Durham, which was opened in 1967, and a 10,666 sq ft store in Pontefract, Yorkshire.
Bond has repeatedly said he is not interested in launching a convenience store format.