Spinach Artichoke Quiche from Simply Recipes. My testing note says ”Delish; also can be crustless.”

Not a quiche, but close. Not really a frittata either. But we love it. If you choose to make this USE A DEEP PAN.

Tomatoes are out of season here, but you might be able to use Campari or some nice grape tomatoes to make it.

I like broccoli, carrots and onions in a veggie quiche, with some fresh herbs. Coincidentally, I have some broccoli & cauliflower I was thinking of using in a quiche or 2, since it needs to be used soon.

Onions and sliced tomatoes are good too.

Another. I never realized I had so many meatless quiches!

I have not personally tested this Cheesy Crustless Quiche, but it is from Simply Recipes, a site I trust. I think you could easily omit the bacon. It seems to be almost a garnish.

If you think decadent and sinful would be fun for them, you can't go wrong with Julia Child's quiche aux champignons. I don't use the extra dots of butter. :)

https://www.atoastandtea.com/mushroom-quiche/

If you think they'd rather have light and tasty to rich and decadent, there's also quiche adjacent:

This is my aunt's recipe for not quiche. Not only does it have no crust, it has no
cream, no butter, and is still a very nice custard.

• 3 midsize onions, sliced and sautéed with a little wine or
  oil

You can substitute any well wilted chopped vegetables for the onions, such as spinach, but make sure the water content is well wept out of them or the custard won't set.

• 3 eggs, well beaten
• 1 2/3 cups scalded milk (or evaporated)
• approx. 2 cups grated pungent cheese, such as gruyere
• approx. 1/4 cup finely grated (powder fine) hard cheese,
  such as parmesan
• salt to taste
• 2 dashes pepper sauce

Mix and bake at 350 F for about 40 minutes (until custard is
set).

I like to make this with baby spinach, or spinach and onions, or spinach and mushrooms. I didn't even remember that it was originally just onions. :)

I don't do much in the way of a recipe for a quiche....I just fill a pie shell with slightly steamed vegetables ( so they have lost some moisture and don't get watery), grated cheese and pour on a mix of milk or light cream...3 eggs to a cup of milk or cream.
So use your imagination....mushrooms, broccoli, spinach ( must be cooked and squeezed very dry not to be watery).....and vary your cheese to suite.
And of course season to taste....a little salt....maybe worchestershire....fresh herbs....lots of parsley....basil....whatever.

What makes quiche nasty is when its watery. If you take a base of 2 whole eggs plus 2 yolks mixed in to about 10 FL oz good cream, your filling will be delicious.

That’s how I make my quiches as well, Linda :-)

Thank you all. Tomato Pie and Peppers,onions and mushrooms Quiche were the veggie ones I added some julienned Prosciutto I had in cheese draw to a third.