This means that 35 per cent of the group's nurseries been given the highest accolade.
Of the eight nurseries, five moved up from good to outstanding, two held on to their outstanding status, and one jumped from a satisfactory to the top grade.
The nursery group has had ten inspections since January, with the other two nurseries moving up from satisfactory to good.
Childbase operations director Lynda Gostelow said, 'With all of these results, the success is down to staff and how well they know the developmental stages of the children in their care.'
She said the group had also carried out bespoke training for settings and had appointed childcare and education experts in each of the three regions.
'We did a lot of work training staff, particularly on working with boys and on role-play and super-heroes. We've supported staff in gaining confidence in their knowledge of the Early Years Foundation Stage.'
She added that changes were also made on children's learning journeys and record keeping, on inclusive practice and on supporting gifted and talented children.
Ms Gostelow said, 'The common thing in feedback from inspectors is that staff really know their children and support them in their individual needs. Inspectors have said that we should be very proud of how well the staff know their children and the feeling that the staff feel part of something bigger.
'What is coming out is how knowledgeable and supportive of children the staff are, and when the inspectors observe their practice, the practice supports the knowledge.'
Most nurseries now have an EYP and the group aims to have 90 per cent of staff qualified to a minimum of level 3 by 2014.
Last month, Childbase opened its 40th nursery in Sandhurst, Berkshire, a 90-place purpose-built setting.
It is also building a new nursery building at a site in Kent housed in temporary buildings, and is opening a new nursery unit at Emscote House School and Nursery in Leamington Spa, which the group acquired last year.
The company is 75 per cent owned by employees. It has just announced its bonus scheme for the year, which will see 1,280 employees share £650,000.
This year, employees will have a bonus made up of two elements, with half related to profit and half based on attendance records.
Staff lose 10 per cent of their bonus for each day they are absent, up to a maximum of 50 per cent.The group's employee share plan started ten years ago, with shares valued at 40 pence now worth £1.14.
- The eight outstanding nurseries named this year are: Lavenders, Bedford; Lime Grove, Hemel Hempstead; Westwood, Coventry; Pennypot, Chobham; Cherry Trees, Cranfield; Field House, Buckingham; Seabrook, Luton; and Knowle Green, Staines (pictured above).