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Preheat oven to 350 degrees.
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Heat oil in a large skillet and add onion, bell pepper, and mushrooms; saute until vegetables are just soft, about 3 minutes. Season with pepper. Add sausage and saute another 2 minutes; let cool to room temperature.
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Sprinkle 1/4 cup shredded Swiss cheese in bottom of pie pan.
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In a large bowl, mix together, remaining 1/2 cup Swiss cheese, spinach, cottage cheese, cheddar cheese, and eggs. Add gluten-free baking mix and stir until blended. Pour into pie pan. Bake 40-45 minutes or until center of quiche comes out clean when a knife is inserted.