Yesterday I made a crustless quiche (I guess it's technically a frittata) for breakfast and it turned out great so I thought I'd share. Here's what I used from what we had in the fridge, but I'm sure you could substitute just about anything on this list and it would work great.
2 small zucchini and 1 small yellow squash, grated
about 6 medium mushrooms
1/2 cup or so of grated pepper jack cheese
two big tablespoons of salsa
some chopped spinach (about a cup)
6 links of chicken or turkey sausage, chopped
salt and pepper
First, I turned the oven to 375 degrees. I grated the squash and then squeezed as much water as I could out of the grated squash with a dishtowel. I put that into a bowl and added everything but the sliced tomatoes and stirred it up until it was mixed well together. I poured that mixture into a greased 13×9 metal cake pan (because I left the glass one at home — this worked just fine though). I arranged the sliced tomatoes on top, did one more pass with fresh ground pepper on top, and stuck it in the oven to bake.
I set the timer for 20 minutes but the middle of the quiche was still jiggly when I moved the pan after 20 minutes, so I rotated the pan and put it back in the oven for about another 7-8 minutes. This will likely depend on your oven (and whether it's a small oven in an Airstream, or your regular oven at home). You want the surface to be tight, and the edges will have started to brown.
Cut and serve! It was great with a little chipotle hot sauce on top, too!