In a large skillet, heat about 1 tablespoon of olive oil over medium-high heat, add bell pepper and onions. Cook until soft, stirring occasionally, 4-5 minutes. Remove from pan onto a clean plate.
Add 1 more tablespoon of oil to the same pan and heat. Stir in chicken and seasoning. Cook until chicken is cooked through and browned, 4-5 minutes. Return peppers to pan and mix to combine.
Spread mayo inside sub rolls and fill with the chicken and pepper mixture. Top each sub with 2 slices of cheese and broil in the oven until the cheese is melted and gooey. Enjoy!