There are 16 ounces in a pound, so about 10 pounds of meat would be necessary to feed 20 people. According to the Food Network, when planning a barbecue or dinner party, there should be about 6 to 8 ounces of meat allocated per adult.
A total of 1 pound of food is recommended per adult, so side dish options are a good idea in addition to the meat. The Food Network also advises that the more options that are offered to guests, the less of each option they will eat. So if a lot of side dishes are offered alongside the barbecued meat, then the amount consumed per person is likely to be closer to 6 ounces rather than 8 ounces. Thus, it may be possible to get away with less meat than 10 pounds.