Preheat oven to 400° F. Butter a 9-inch pie dish.
Place the frozen broccoli, peppers & onion in a large microwave-safe bowl. Add ¼ cup of water. Cover and microwave on high for 5 minutes, stirring halfway through. Drain all liquid (this is key) and cut any large broccoli or pepper pieces.
In a large bowl, whisk together the eggs, sour cream or Greek yogurt, kosher salt, black pepper, garlic powder, and onion powder. Gently stir in the veggies and cheese.
Pour the egg mixture into the buttered pie dish. Bake about 30 minutes or until the quiche is golden-brown. Insert the tip of a knife in the center of the quiche to test doneness – the knife should come out clean.
Allow to cool and rest for about 15 minutes.
Slice, serve, enjoy!