This is something super simple that everyone loves!
1/2 green pepper, diced
1/2 onion, diced
1 pkg mushrooms (we like a lot of mushrooms!)
3 tbsp Italian dressing
6-oz pkg deli-sliced roast beef
Saute the green pepper and onion in some olive oil. Season with salt and pepper while cooking. After a couple minutes, add the mushrooms. Once all the veggies start to soften, add the Italian dressing and roast beef. Let it all cook and warm through. Serve on hoagie buns (it usually makes 5 sandwiches when we have it). You can add some provolone cheese if you'd like as well.