Chicken Philly Sub Sandwiches

3 tablespoons butter
1 brown onion
1green bell pepper
1 package boneless, skinless chicken
liquid steak marinade
mozzarella cheese slices
sub sandwich rolls

1. Quarter and slice onion and bell pepper. Cut chicken into small slices, or dice largely.
2. Place butter, onion, bell pepper, chicken and marinade in crock pot. Stir to coat.
3. Cook on low at least 5 hours.
4. Serve on rolls with cheese slices.