The Guardian recorded a combined readership of 8.96 million in what is now the third release from the NRS PADD report.
When the report was first launched in September, the Guardian also had the highest combined readership among 'quality' newspapers, with 8.95 million.
But while this figure rose to 9.16 million in the next release of the data, a month later, the Guardian was overtaken by the Telegraph, which recorded 9.23 million monthly readers in print and online.
Now the Guardian has regained the top spot for monthly combined readership, with the Telegraph just behind with 8.88 million readers.
Chief commercial officer at Guardian News & Media David Pemsel said in a release that "the latest NRS PADD data confirms us as Britain's most successful quality newspaper brand – highlighting the power of our digital-first and open strategy."
The latest report is based on print readership figures from the NRS from October 2011 to September 2012 and online data from UKOM/Nielsen for September 2012.
While the Guardian was top for monthly readership, the Telegraph kept its lead for weekly and daily readership, with combined readerships of 4.57 million and 1.9 million respectively.
This compares to a weekly combined readership for the Guardian of 4.54 million, and a daily readership of 1.58 million.
The Sun still has the highest monthly combined readership across all national daily UK newspapers in the report, with a readership of 17.32 million.
The data does not include international readership or those accessing websites from devices such as smartphones, tablets or apps. The online figures are also measured by person using surveys, and not by browser.
Releases from the report next year will be delivered quarterly.