I have seen that we will be having a barbecue over Shavuot. How is it possible to make a barbecue on Yom Tov?
That is a great question! First, it is important to understand that, although the rules of Shabbat and Yom Tov are very similar, cooking for that day is permitted (among other exceptions) on Yom Tov based on the verse in Shemot 12:16.
In some ways, making a barbecue is the simplest way to cook on Yom Tov – one does not have to worry about timers or sensors or other gadgets often used on modern ovens that can create halachic difficulties. The two main Yom Tov issues one needs to watch out for with regards to the BBQ are lighting a new fire and extinguishing a fire (both of which are prohibited).
With regards to lighting a fire, one needs to make sure that the initial flame comes from an already existing fire (like a 24-hr candle). For a coal or wood barbecue, just light a splint or similar from the candle and use that to ignite the coals/wood. Fanning the flames or moving the coals/wood to help them catch is completely permitted. For a gas barbecue, simply turn on the gas, taking care not to ignite a spark as you turn the knob, and use the pre-existing flame to light it.
Extinguishing a fire is a little more challenging – as a general rule, it is forbidden to turn off a fire or lower a flame on Yom Tov. The reason for this is that there is no cooking need to do so – if one needs a smaller flame, simply make a smaller one and if the food is burning, one can simply take it off the fire. Nevertheless, Rav Moshe Feinstein writes that this was said at a time when making a fire smaller would involve multiple violations and the simple act of creating a new flame was halachically preferable. Nowadays, he says, when turning a knob up or down is the same sort of act, raising and lowering the flame would be permissible when cooking.
Once the cooking is finished, it is halachically problematic to turn off the fire but it is also not safe to leave it burning unattended. In a Shul setting, the caretakers are able to turn off the flame, as this is considered a necessity, although they should be asked to do so before Yom Tov begins. If one can set up a similar situation at home, that is ideal. Another alternative is to use a small or nearly empty tank that will go out on its own after a short time. A coal barbecue can simply be allowed to burn out on its own.
It should go without saying that in cases of immediate danger, turning off the fire, or indeed any other violation of Yom Tov should be done swiftly, as with any life-threatening situation. Nevertheless, one should do what is possible to avoid finding oneself in such a situation and set up safety measures in advance.
Finally, it is best to prepare what one can before Yom Tov if it will not lower the quality of the food. Clearly barbecued meat is significantly better straight off the grill than when refrigerated and reheated!