Prepare the chicken. Thinly slice the chicken breasts and set aside.
Cook veggies. Heat a large skillet, then add the sliced mushrooms, peppers, and onion with oil and butter. Sauté over high heat until the vegetables are slightly tender, then remove from the skillet.
Cook chicken. To the same skillet, add the sliced chicken and saute until cooked through. Once the chicken is cooked, add the vegetables back to the pan.
Season. Add minced garlic and seasoning to the pan and toss. Turn the heat down to low.
Cheese. Top the chicken with slices of provolone cheese, cover the pan with a lid, and let the cheese melt.
Toast bread. Slice the hoagie buns and toast until golden. Spread a layer of mayo on each side.
Assemble. Divide the cheesy chicken and veggies between the buns with the cheese facing up. Close the hoagies, slice, and enjoy!