4 medium/large wide zucchini (2 1/2 lbs)*
3 Tbsp olive oil, divided
1 large yellow onion, sliced into short pieces
8 small button mushrooms (6 oz), sliced
1 large red or green bell pepper, chopped into short slices (or 1/2 of a red 1/2 of a green)
3/4 lb sliced thin deli roast beef, chopped into small pieces
Salt and freshly ground black pepper
1 1/2 Tbsp water or beef broth
1 1/4 cups shredded provolone cheese
Chopped fresh parsley, for serving
Preheat oven to 400 degrees. Using a spoon, scoop centers from zucchini to create boats while leaving a 1/4-inch rim (reserve centers for another use). Brush both sides of zucchini with 1 Tbsp of the olive oil and season lightly with salt. Place in two baking pans (I used a 13 by 9 and 8 by 8). Bake in preheated oven 20 – 25 minutes until nearly tender.
Meanwhile, heat 1 Tbsp olive oil in a large non-stick skillet over medium-high heat. Add onion and saute 5 minutes, then add another 1/2 Tbsp olive oil and mushrooms and saute 5 minutes longer. Push veggies to one side of pan then add remaining 1/2 Tbsp olive oil to opposite side, add bell pepper and garlic and saute until tender, about 3 minutes. Add in roast beef, season with salt and pepper to taste then stir in water and cook until warmed, about 30 seconds.
Fill roasted zucchini with roast beef mixture. Sprinkle top evenly with cheese. Return to oven and bake about 5 minutes longer, or until cheese has melted. Serve warm garnished with parsley (fyi these are easier to just pick up and eat by hand like a sandwich).
*You can also make these into the classic Philly Cheese Steak Sandwiches by using 4 hoagie rolls in place of the zucchini and upping the roast beef to 1 lb.