Prepare all vegetables: shred the lettuce, slice the onion, halve the tomatoes, and chop the peppers.
Add the vegetables, deli meats, and shredded cheese into a large mixing bowl.
In a separate small bowl, whisk together mayonnaise, red wine vinegar, olive oil, garlic powder, Italian seasoning, salt, and pepper until creamy.
Pour the dressing over the salad ingredients. Toss well until evenly coated.
Serve immediately, or let the salad chill in the fridge for about 10 minutes before serving for the best flavor.