Set your oven to 350°F (175°C). Lightly grease a 9-inch pie pan or 8×8 baking dish with olive oil or cooking spray. This prevents sticking and ensures easy slicing later.
Heat olive oil in a skillet over medium heat. Cook diced onion and bell pepper until soft, about 3–4 minutes. Add chopped spinach, cook until wilted, and season with garlic powder, salt, and pepper.
In a large bowl, whisk eggs, milk, and cottage cheese together. Add Italian seasoning, salt, and pepper. The cottage cheese will remain slightly lumpy, giving creamy pockets in the quiche.
Gently fold sautéed vegetables and shredded cheese into the egg mixture. Make sure everything is evenly distributed for consistent flavor and texture.
Pour mixture into the prepared pan. Tap gently to release air bubbles. Bake for 40–45 minutes until golden brown and fully set. A knife inserted should come out clean.
Let the quiche cool 5–10 minutes before slicing. Cooling helps maintain clean, firm slices without being runny.