Reply To: Dunkin Donuts Muffins

Do they bake treifos in the same oven as these items?

If they’re baking cheese bagels in the same oven, then that may not be a concern necessarily, since cheese uses vegetarian or microbial rennet, and is actually kosher per the shita of Rabbeinu Tam (Tosfos Avodah Zarah 35b, s.v. chada). R’ Soloveitchik held like R’ Tam, le chatchila.

Furthermore, from Pesachim 76b, the Ran says that Levi permits the roasting of the kosher meat in the same oven as the non-kosher even Le chatchila. This is borne out by the Talmud Yerushalmi (Terumos 10:2) which says so explicitly. The geonim and most of the rishonim pasken like Levi be dieved.

In the machlokes Rav and Levi, most hold like Levi- reiach from an oven is insignificant, and such food is kosher; see Rambam, Maachalot Asurot 15:33; Rif, Chulin 32a and Rashi, Pesachim 76b s.v. amar lecha, even if only be dieved.

We are still left with issues of pat yisrael and bishul akum, though.