In a large Ziploc bag, combine the chicken breasts & marinade. Seal & place in the fridge to marinade for at least 30 minutes up to overnight depending on the amount of flavor you want the chicken to have - I did overnight.

Spray a 3-4 quart slow cooker with cooking spray. Set temperature to low.

Add the butter, sliced onions & sliced peppers to the bottom of the slow cooker. Empty the contents of the Ziploc bag of chicken into the slow cooker on top of the onions & peppers.

Cover & cook for 4-5 hours or until chicken can be easily shredded.

Serve on the hoagies with a slice or two of melted mozzarella on top. I melted my cheese under the broiler in the oven for a minute or two.