In 12-inch skillet, melt butter over medium-high heat. Add onion; cook until tender. Add mushrooms; cook until tender. Stir in chicken, roasted peppers and Alfredo sauce. Spoon about 2 1/3 cups chicken mixture in baking dish. Layer with 3 noodles, half of cottage cheese mixture and 1/2 cup of the mozzarella cheese. Repeat layers. Top with remaining 3 noodles, 2 1/3 cups chicken mixture and 1 cup mozzarella cheese.