In the same skillet, add the remaining tablespoon of olive oil. Sauté the onion, bell peppers, mushrooms, and garlic until the vegetables soften and become fragrant. Add the cooked beef back into the pan, stir everything together, and taste to adjust the seasoning if necessary.
3. Build the Quesadillas
Spread a thin layer of mayo on each tortilla if desired. Evenly distribute the beef and vegetable mixture over them. Lay slices of Provolone cheese on top and sprinkle with the Mexican cheese blend. Fold each tortilla in half to create the quesadillas.
4. Toast Until Crispy