In a jar with a lid, add the lemon juice, Dijon mustard, red wine vinegar, sugar, dried oregano, olive oil, kosher salt, and black pepper. Secure the lid and shake for 10 seconds until thoroughly combined. Taste and adjust seasonings if necessary.

Add the chopped romaine to a large bowl and drizzle with a few tablespoons of the vinaigrette.

Top the romaine with red onion, chickpeas, cherry tomatoes, mozzarella, pepperoncini, roasted red peppers, and basil. Stir together well before serving. Add more dressing if desired.