It was composed around 845 CE and probably called "rabbati" (the larger) to distinguish it from the earlier Pesikta de-Rav Kahana (PdRK).
Pesikta Rabbati has five entire piskot (sections) in common with PdRK—numbers 15 ("Ha-Hodesh"), 16 ("Korbani Lachmi"), 17 ("Vayechi ba-Hatzi"), 18 ("Omer"), 33 ("Aniyyah So'arah"), and the majority of 14 ("Para")—but is otherwise very different from PdRK; it is similar to the Tanhuma midrashim.
In 1880, Meir Friedmann edited a version of the Pesikta Rabbati[1] which contains, in 47 numbers, about 51 homilies, part of which are combinations of smaller ones; seven or eight of these homilies belong to Hanukkah, and about seven each to Shavuot and Rosh Hashana, while the older PdRK contains one each for Hanukkah and Shavuot and two for Rosh Hashana.
There are also various differences between these two Pesiktot in regard to the Torah readings for holidays and for the Sabbaths of mourning and of comforting.
46, which is of foreign origin), which have the superscription "Midrash Harninu"—a name used to designate the homilies for Rosh Hashana and Sukkot which the old authors found in the Pesikta Rabbati.
46 is a foreign addition; here Psalms 90:1 is interpreted as an acrostic למשה (ascribed to Moses), and there is also a passage from the Midrash Konen.
In the beginning of the first homily, which shows the characteristics of the "genuine" portions of the Pesikta Rabbati (in the proems of R. Tanhuma following the halakic exordium), the year 845 is indicated as the date of composition of the work; there are no grounds for regarding the date as a gloss.