Is it permitted to take frozen vegetables from the freezer on Shabbat morning and place them on the blech to eat them at the seudah?
In general is frozen food muktzeh?
Please send sources
Frozen food is not mukzeh, because it can be taken out of the freezer and eaten.
For frozen meat, see the Shulchan Aruch (308:31), where the ruling is lenient because the meat can be consumed raw. However, several poskim, including the Ben Ish Chai, Aruch Ha-Shulchan, Iggros Moshe, and Rav Shlomo Zalman Auerbach zt”l, rule that today one must be stringent, because nobody eats or uses raw meat.
Even if the frozen vegetables are fully pre-cooked, it is still not permitted to put them directly onto the blech. Rather, they can be placed next to a fire, or placed on top of another pot filled with food (see Biur Halacha 253:3 s.v.veyezaher) on the fire. The idea is that the warming should be done in such an atypical manner that everyone will realize that this constitues a case of warming, and not cooking, the food (also, the oddity of the situation will remind the person not to raise the flame).
According to the Iggros Moshe, it will also be permitted to place the vegetables directly on a hot-plate that cannot cook but only retain heat, provided its heat buttons are covered up.