Heat olive oil in a skillet over medium-high heat. Season chicken with salt and pepper; cook in hot oil until browned, 3 to 5 minutes. Stir onion and mushrooms with the chicken; continue cooking until the onion is translucent, 5 to 7 minutes. Pour cream of mushroom soup and Marsala wine over the chicken mixture; cook until hot and the chicken is no longer pink in the middle, 3 to 5 minutes.
