... is an interesting one. Found in the Leonine, Gregorian, and Gelasian Sacramentaries, it settled comfortably into the 'Green' season; Pentecost VIII in the Tridentine Rite but Trinity IX in many Northern European dialects of the Roman Rite, including Sarum, York, etc..
First point to note: the Bugnini revisers, having taken the fervour out of Lent, found the old Lenten collects too fierce and drafted into use to replace them collects from Ordinary Time.
Secondly, there is a textual oddity. Largire nobis, quaesumus, Domine, semper spiritum cogitandi quae recta sunt, propitius et agendi ... "Propitius" is a common word in liturgical Latin, which borrows it (I have Christine Mohrmann in mind here) from pagan liturgical Latin. It means that the Deity is or has been rendered favourable to the suppliant. Problem: it is separated from noun which it adjectivally qualifies - Domine - and dropped into mid-sentence. This is by no means impossible (" Grant to us, we beseech thee O Lord, ever the spirit of thinking the things which are right, and, being favourable, of doing them ..."), but it is pretty well as odd in Latin as it is in English. Cranmer found it so and simply left it out.
One of Bugnini's men had - or found somewhere - a very clever idea. Perhaps the word is a scribal corruption. m was often reproduced in abbreviation by a line over the previous vowel. This line could easily not be noticed in transcription. So if the original had read "promptius", that could easily appear as "proptius" - which is non-existent - and then be "corrected" to the very common " propitius".
"Promptius" would mean "and rather more promptly". So the prayer would mean that we desire the spirit of thinking good things; but not just of thinking them: of also getting on and doing them rather more quickly. I 95% buy it!