Cut the chicken into 2 1/2 to 3" pieces (almost like half a chicken tender).
Put olive oil into a large skillet pan and heat up to medium-high.
Add chicken pieces to the hot pan and sprinkle with ground oregano (flakes will work but the taste is a bit better with ground), sea salt and pepper. Cover and let sauté for about 3 minutes.
Turn the chicken pieces over, add the mushrooms and onions tucked all around the chicken pieces. Sprinkle whole dish with remaining oregano, sea salt and pepper. Cover and let sauté for another 4 minutes or so.
Stir until all onions, mushrooms and chicken appear to be tender, usually about a total of 7-8 minutes.
Turn down to about medium heat and add the marsala wine, give it a rapid simmer for another 5 minutes. Add 1 tablespoon of low fat sour cream, stir in, cover and take the dish off the burner to allow to cool some.
There are 221 calories in 1 serving of Chicken Marsala II.