Place half of mushrooms in a quart jar. Add 1 1/2 teaspoons salt, 1 1/2 teaspoons sugar, 1 tablespoon onion, 1 clove garlic, 1/8 teaspoon white pepper, 1/8 teaspoon red pepper, 1/8 teaspoon oregano, 1 cup vinegar, and 1 cup oil. Cover and shake to mix well. Repeat procedure with remaining ingredients in a separate jar. Refrigerate overnight. Serve with a slotted spoon.
Note: Herbed Mushrooms may be prepared up to 1 week ahead of time.