If one davens at a minyan that (during the winter) regularly begins shachris before the zman for talis & tefillin & the zman always arrives during pesukei d’zimra–is it better to put them on with a beracha during pesukei d’zimra (bein haperakim) or to wait until between yishtabach & barchu?
Under such circumstances, the best course of action would be to begin Pesukei Dezimra with Hodu (as in Nusach Sefard, which is also the ruling of Tur), and to make the blessings before one gets to Baruch She’amar.
If this is not practical, one should wait until after Yishtabach, though several poskim permit putting on the tallis and tefillin earlier, and one who does so has much to rely on.
Sources: Shulchan Aruch (Orach Chaim 53:3) writes that one should not interrupt Pesukei Dezimra to make the blessing over tallis and tefillin, but rather one should wait until after Yishtabach. However, Rabbi Akiva Eiger (in his glosses to Shulchan Aruch) writes that this possibly applies only at the end of Pesukei Dezimra, but not in the middle (explaining this in the opinion of Levush), and concluding that the halachah remains unclear. Yet, we find explicitly in a teshuvah of Rambam (Pe’er Hador 147) that one may recite the blessings during Pesukei Dezimra, a ruling that it quoted by Birkei Yosef (53:4 — arguing with Ginas Veradim 1:53). Although Maamar Mordechai writes that in the opinion of Shulchan Aruch one may not interrupt during Pesukei Dezimra, it would seem that there is sufficient room to rely on the authorities above, and to recite the respective blessings. This is also the ruling given by Halachah Berurah. Yet, based on the silence of Mishnah Berurah and others, the basic halachah would remain that one should wait until after Yishtabach.