In a medium bowl, whisk together the garlic, salt, black pepper, oregano, mayonnaise, sugar, and apple cider vinegar until smooth.
While whisking constantly, slowly drizzle in the olive oil until the dressing is fully emulsified and creamy.
In a large salad bowl, combine the lettuce, bell pepper, grape tomatoes, cucumber, red onion, pepperoncini, and Parmesan cheese.
Pour the dressing over the salad and toss well until everything is evenly coated. Serve immediately, or refrigerate the dressing separately until ready to serve. If the dressing separates as it sits, simply shake or whisk it again before using.
