Prepare any side you'd like to accompany this chicken marsala recipe; set aside.
In a small bowl, mix together the flour, salt, pepper and oregano. Coat thinly sliced chicken pieces in flour mixture.
In a large skillet, melt butter in oil over medium heat.
Place chicken in the pan, and lightly brown on both sides, about 5 minutes each side.
Remove chicken pieces to a plate. Add mushrooms and sauté for 1 minute. Pour in wine and sherry. Bring to a small boil, add chicken back to pan.
Cover skillet; simmer chicken 10-15 minutes, turning once, until no longer pink and juices run clear. Season with additional salt and pepper if needed.
Serve with optimal pasta, mashed potatoes or salad. Enjoy!