1. Preheat oven to 350°. Place shredded potatoes in a large bowl; add cold water to cover. Let stand 5 minutes; drain and pat dry.
2. Melt butter with oil in a 10-inch cast-iron skillet over medium heat. Add bell pepper, onion, and mushrooms, and sauté 3 to 5 minutes or until tender. Add garlic; sauté 1 minute. Stir in shredded potatoes and 1/2 tsp. salt; cook, stirring often, 10 minutes or until potatoes are golden and tender.
3. Remove from heat, and stir in olives and sun-dried tomatoes.
4. Whisk together eggs, pepper, and remaining 1/4 tsp. salt; whisk in Swiss cheese. Pour egg mixture over potato mixture in skillet.
5. Bake at 350° for 9 to 10 minutes or until set. Cut into wedges, and serve immediately.
*3 cups firmly packed frozen shredded potatoes may be substituted, omitting Step 1.