Slice ribeye into thin strops. Cut bell peppers into long strips, onion into half rings and mushrooms into bite-sized pieces.
Preheat an oiled skillet over high-heat. Add onions, bell peppers and mushrooms to the skillet. Sautee until all veggies are golden brown. Remove from the skillet and set aside.
Add sliced beef to the same skillet and season with salt and pepper. Sautee until the beef is fully cooked. Add vegetables back to the skillet and stir to combine. Top with cheese slices and let mixture sit for a minute to melt.
Stuff toasted or untoasted hoagie buns with the mixture. Serve immediately and enjoy!