If I bake cookies in a Fleishig oven which had chicken in it during the last 24 hours but NOT at the same time as the cookies, can I eat the cookies with milk?
If there is any grease of the Fleishigs remaining on the walls of the oven, one may not eat the cookies with milk. Even if the oven was completely clean, one may not eat it L’chatchillah with milk, unless the chicken was completely covered when cooking. If it was, however, already mixed with milk it may be eaten in both scenerios. One may have milk before or after.
See here:
http://www.halacha2go.com/php/h2go/home2.php?number=622
Sources:
רמ״א יו״ד סי׳ צה סעיף ב ובנו״כ שם.
ולהעיר שלפעמים קשה לבדוק שהתנור נקי לגמרי משומן של בשר
