Chop the pepperoni, cheese, mushrooms, and bell pepper into 1/2-inch cubes and place in a medium bowl. Slice the tomatoes and olives in half and add. Thinly slice the onions and pepperoncini and add to the bowl.In a small bowl, whisk together the oil, vinegar, minced or pressed garlic, Italian seasoning and salt. Pour the dressing over the vegetables, and fold together until all pieces are well coated. This salad can be eaten immediately, but gets even better after a few hours in the refrigerator. Refrigerate for up to 5 days. Each serving is about ¾ cup salad.