Prep: Preheat the oven to 350° F. Grease an 8x8-inch nonstick metal pan or glass/ceramic dish (butter works best to reduce sticking).
Saute Bacon: In a medium nonstick skillet, cook the diced bacon over medium-high until crisp, about 5-7 minutes. Use a slotted spoon or spatula to transfer the cooked bacon to the casserole dish. Drain off almost all of the grease, leaving 1-2 teaspoons.
Saute Veggies: Add the green onions, chopped spinach, garlic, and red pepper flakes. Saute for about 1 minute or until the onions and spinach are wilted and the garlic is fragrant. Be careful not to burn the garlic. Add the onion/spinach mixture to the bacon in the greased casserole dish.
Make Egg Mixture: In a medium mixing bowl, whisk together eggs, 3/4 cup shredded cheddar (reserve 1/4 cup), Parmesan, and pepper.
Assemble Casserole: Pour the egg mixture over the top of the casserole and stir together with the bacon/veggies until everything is evenly distributed throughout. Sprinkle the remaining 1/4 cup cheddar cheese over the top of the casserole. (Freezing instructions begin here.)
Bake: Bake on the middle rack for about 25-30 minutes (nonstick metal pan) or 35-40 minutes (glass or ceramic pan), until the middle is set, rotating the pan around. Do not overcook! Let cool for 5-10 minutes. Then slice and serve warm. Leftovers can be stored in the fridge for up to 5 days.
Freezer Instructions
To Freeze: Put quiche together (through Step 5) but do not bake. Cover tightly with plastic wrap and/or foil. Carefully place in the freezer.To Prepare: Thaw about 24 hours in the refrigerator. Bake according to directions.
Notes/Tips
Do not add more bacon or cheese--it will make it too salty if you do.
I recommend the metal pan over glass. It cooks more evenly and stays moist. I used this Caraway 9x9-inch square pan which I highly recommend investing in! This pan bakes faster, though, so it will only take about 22-23 minutes.
To test if it’s cooked through, insert a knife in the center of the egg casserole and ensure it comes out clean.