What to cook for guests who can't eat dairy, meat, onions, garlic, gluten, beans & more?

You could make a version of Imam Bayildi (Turkish eggplant--halve and scoop out the interior of eggplant, dice, and sauté with diced peppers and tomatoes, stuff this mixture back into the eggplant shells and bake until browned and bubbly). You can build flavor by browning well. Make salads topped with roasted mushrooms (crisp-roasted sliced hen-of-the-woods, or shiitake, with an "x" cut into the caps, have a rich meaty flavor)

pablum

With that many constraints, I would ask all of them. What one may be able to eat one or two may not be. BB

Make it a potluck. That way, guests are sure to bring something they can eat. I like the idea of grilling (poultry, seafood, tofu, veggies) a main and maybe having a variety of sauces for dipping/pouring on the plain grilled items.
I'm with you though: I can understand food allergies (I can't digest onions or garlic) but I don't expect anyone to tailor their menu to me. I take my enzymes and eat around the problem food.
It does feel as if some people are now becoming afraid of food. And in my mind, real food is one of the joys of life!

It all depends on the meaning of "meat" and "& more" but grilled vegetables are wonderful things with only salt and olive oil. Eggplants are your friends and "meaty" vegetables like pumpkins and squash can happily fill any stomach on a summer evening.

Does "meat" include sea food? If you can serve seafood, that's another whole world of things that work very well salted and grilled.

My suggestion is to have a hot griddle over your gas grill outside and just empty a vegetable cart on it. Go tapas style, so individual restrictions don't limit everyone.

Good luck.

This time of year a protein and veggies on the grill are simple and delicious. It also rules out most of the food your guests can't eat.

Ask them what they suggest and find your own interpretation of those dishes. It's difficult to give recipes when "more" is a restriction.

Fish with rice or potatoes, and a veggie or salad