Surprise 30th Birthday Marinade

So this really isn't the name for this marinade. I have no idea what the name is. I gave it this name since it was the marinade used on the mountain of chicken Wendy made for my surprise 30th birthday party. It's good and I like anything that has less than 5 ingredients! (any spicy brown mustard tastes good in this!)

4 chicken breasts (cut in strips if kabobing)

1 packet good seasons dry Italian dressing

¼ c red wine vinegar

½ onion diced

¼ cup grey poupon mustard (add more if needed to thicken)

Mix in bowl and then pour over chicken and marinade.