Combine flour, salt, pepper and oregano and blend well. Heat the oil and butter in a skillet until bubbling lightly. Dredge the chicken in the flour and shake off the excess. Cook the chicken on medium heat for about 2 minutes on the first side, until lightly brown. As you turn the breasts to the second side to cook, add the mushrooms around the chicken pieces. Cook about 2 more minutes, until lightly browned on the second side. Stir the mushrooms. When the second side is lightly browned, add the wine around the pieces, cover the pan and simmer for about 10 minutes.