In a medium skillet cook red onion and garlic in hot oil until tender but not brown. Add the endive or spinach and crushed red pepper. Cover and cook over low heat for 2 minutes.
Place bread shell on a 12-inch pizza pan or large baking sheet. Sprinkle Swiss cheese evenly over bread shell. Top with endive mixture and toasted nuts. Sprinkle Colby cheese over the top. Bake in a 425 degree F oven about 10 minutes or until cheese melts. Cut into wedges. Makes 4 servings.