Most of the Greek texts found in Qumran come from cave 4 and cave 7. Identified Greek texts found in cave 4 are mainly translations of Torah (for example,
4Q119 aka 4QLXXLev[sup]a[/sup] and
4Q120 aka 4QpapLXXLev[sup]b[/sup], which are fragments of Leviticus, or
4Q122 aka 4QLXXDeut, Deuteronomy). Cave 7, in fact, had nothing but Greek texts written on papyrus, but most of these are too fragmentary to be identified precisely, leading to all sorts of speculation. (The texts which a few people allege were fragments of the NT are from cave 7.) The only two fragments in which many are in a consensus are
7Q1 aka papLXXEx (Exodus 28) and
7Q2 aka papLXXEpJer (the Letter of Jeremiah).
That being said, there is no proof that Greek was actively used by the Qumran sectarians. Based on the fragments of the Old Greek LXX found in those caves, it is possible that some of them knew Greek. But cave 4 probably served as a depository of some kind (not a library) in which the sectarians placed all their written texts (mainly Hebrew and Aramaic literary works, but also
tefillin and
mezuzoth). The depository in cave 4 contained eight Greek texts, which may signify that the person(s) who brought these texts to Qumran had used them prior to their arrival, thus implying knowledge of Greek. However it is not impossible that these texts directly came from an archive. The evidence does not suggest that the Greek texts from cave 4 were written, read or consulted at Qumran. As for cave 7, the contents of that cave, which was possibly used for lodging or as a workplace, were probably brought directly to the cave from an archive outside Qumran or from a specific site within the Qumran compound. No relation between the Greek texts of caves 4 and 7 need to be assumed, and there is no reason to believe that any of these texts was found in Qumran.
More Greek texts were found elsewhere in the Judaean desert:
Wadi Daliyeh (1 + [undeciphered]), Jericho (17 and several fragments), Wadi en-Nar (2), Wadi Ghweir (1),
Wadi Murabba’at aka Naḥal Darga (71), Wadi Sdeir aka Naḥal David (2),
Naḥal Ḥever aka Wadi Khabra (32 from cave 5/6; 2 from cave 8; 21, and many unidentified fragments from “XḤev/Se” and “Ḥev/Se”?),
Naḥal Ṣe’elim aka Wadi Seiyal (2),
Naḥal Mishmar aka Wadi Mahras (1), and Masada (remains of probably 11 texts [a few in either Greek or Latin] and several fragments). When we compare Qumran to these sites, we could see that the situation is different. In most sites, all the Greek texts (and in Wadi Murabba’at and Masada, the great majority) are documentary, showing that Greek was actively used among the persons who deposited the texts. These texts include documents showing that the administration was conducted in Greek in the provinces of Syria, Arabia, and Judaea, and that letters were written in that language (cf. the Greek letters written by Bar Kokhba’s followers from the Cave of Letters in Naḥal Ḥever). The difference between these sites and Qumran is partly chronological (most of the sites in the Judaean Desert are from a later period than Qumran), but more so in content: the Qumran corpus is mainly religious, which at that time would involve only Scriptural texts in Greek and not other compositions.
P.S. I should note that the Minor Prophets scroll (8ḤevXII gr) comes not from Qumran, but from Naḥal Ḥever. The Naḥal Ḥever scroll actually seems to have been systematically ‘corrected’ to correspond more closely to the proto-Masoretic Text; even the ordering of the prophets follows the traditional Hebrew order, not that of the Septuagint. The fact that this scroll was found among the remains of Bar Kokhba’s followers, linked to the Jeursalem religious circles, is not without importance. It probably implies that this text had the imprimatur of the rabbinic circles.