The watchdog endorses institutions' checks on standards in a report that assesses 76 university audits conducted between 2007 and 2009.
The thumbs-up follows concerns in previous years about grade inflation in some subjects, which could have undermined the guarantee of institutional excellence for all courses. But the QAA says greater "regulatory clarity and the more systematic use of cross-institutional classification algorithms" had allayed these fears.
Overall, QAA auditors made 219 recommendations for improvement and noted 81 features of good practice across the 76 institutions.
Peter Williams, former chief executive of the QAA, said: "The aberrations are comparatively few and rarely very serious. It seems to suggest that quality assurance is being dealt with maturely and effectively.
"This is reassuring for the public, but it is exactly the kind of reassurance that will disappear if the QAA's institutional reviews are invoked only when failures actually happen."
The report does criticise some off-campus provision of courses.
Although most institutions have a good system of checks for collaborative provision, a handful need to improve monitoring, programme approval and review processes, the QAA says.
"In respect of programme approval, in particular, there were proportionately more negative comments in relation to collaborative provision," the report says.
Also highlighted are patchy implementation of academic standards, delays in completing reports, confusion over foreign governments' demands and an absence of credit mapping for vocational courses.
There is also some worry over "the lack of a defined role for external examiners in this context, a lack of policy relating to examiners for provision common to on-campus and collaborative delivery and lack of clear guidance on the appointment of local external examiners by a collaborative partner".
However, Mr Williams said, a separate and fuller audit of collaborative provision had given a more positive view of performance.
A second report published last week by the QAA references 79 examples of good student support across the universities audited, compared with calls for more action. One area identified for improvement is the level of personal tutor support for students.