Remove stems from mushrooms and use a spoon to scrape out the gills. Arrange on a baking sheet, brush with olive oil and season with salt and pepper. Set aside. In a saute pan over medium heat, brown the sausage. Remove from pan. Add 1 tablespoon olive oil. When hot, add the onions and bell peppers, season with salt and pepper. Saute until they have released their water and water has evaporated, and they are soft and starting to turn golden.