1/4 cup all-purpose flour for coating
1/2 teaspoon salt
1/4 teaspoon ground black pepper
1/2 teaspoon dried oregano
4 skinless, boneless chicken breast halves - pounded 1/4 inch thick
4 tablespoons butter
4 tablespoons olive oil
1 cup sliced mushrooms
1/2 cup Marsala wine
1/4 cup cooking sherry