Preheat your oven to 350°F. While it heats, prepare all your vegetables: slice the mushrooms into 1/4-inch pieces, dice the red bell pepper into small pieces, and cut the broccoli florets into bite-sized pieces. Chop the green onions finely and set aside. Make sure your eggs are at room temperature—this helps them blend smoothly and cook more evenly throughout the quiche. Having everything prepped and ready will make the next steps seamless.

Heat the extra virgin olive oil in a large skillet over medium-high heat. Add the mushrooms, bell pepper, and broccoli, stirring occasionally, and cook for about 5 minutes until the vegetables are just tender but still have a slight firmness to them. The broccoli should be bright green and the mushrooms should release their moisture. Remove the pan from heat and let the vegetables cool to room temperature—this prevents them from cooking the eggs prematurely when mixed together.

In a blender or food processor, combine the eggs, cottage cheese, salt, and ground black pepper. Blend until smooth and well combined—this creates a creamy, uniform base for your quiche. I like to blend it well because any lumps in the cottage cheese can create an uneven texture. If you don't have a blender, you can whisk the eggs together and then fold in the cottage cheese gently, though blending gives a smoother result.

Lightly spray or grease your 9-inch pie dish. Pour the egg and cottage cheese mixture from Step 3 into the prepared dish. Now add the cooled sautéed vegetables from Step 2, half of the shredded cheddar cheese, the cooked breakfast sausage, and the green onions directly into the pie dish. Using a spatula or spoon, gently spread and push down the fillings so they're distributed evenly throughout the egg mixture and everything is submerged—this ensures even cooking and a balanced flavor in every bite. Top with the remaining cheddar cheese, distributing it evenly across the surface.

Place the pie dish on a baking sheet (this makes it easier to handle and catches any potential drips) and transfer to the preheated 350°F oven. Bake for 50 to 60 minutes, until the quiche is golden brown on top and the center is set but still has a slight jiggle when gently shaken. The internal temperature should reach about 160°F when measured with an instant-read thermometer in the center. If the top starts browning too quickly, loosely tent with foil for the remaining baking time.

Remove the quiche from the oven and let it rest at room temperature for 15 minutes. This resting period allows the eggs to fully set and makes the quiche much easier to slice cleanly without falling apart. After resting, slice into wedges and serve warm or at room temperature. The quiche will continue to firm up slightly as it cools.