Lightly coat a 9x13 baking dish with the olive oil.

Brown the turkey sausage in a large nonstick skillet over medium-high heat, breaking it into crumbles, until fully cooked, about 6 to 8 minutes.

Dice the red bell pepper and add it to the skillet for 3 minutes. Add the spinach and stir until it wilts, about 1 minute. Spread the mixture evenly in the baking dish. Slice the green onions and scatter them over the top.

Blend the cottage cheese in a blender until smooth. Add the eggs, egg whites, dry mustard, garlic powder, salt, and pepper and blend a few seconds more, or whisk well in a large bowl.

Pour the egg mixture over the filling and sprinkle the cheddar on top. Cover tightly and refrigerate overnight, up to 24 hours.

In the morning, heat the oven to 350F and let the dish sit on the counter while it heats. Bake uncovered for 45 to 55 minutes, until puffed, golden at the edges, and set in the center, 160F on a thermometer.

Rest 10 minutes, then cut into 8 squares.