Mom's Italian Vegetable Salad recipe has changed over the years. This version is the most "from basics" version I've seen.
Toast bay leaf and pepper. Combine vinegar, olive oil, salt, sugar, pepper flakes, and oregano in a pot and bring to simmer. Add bay leaf and peppercorns. Steep 5 minutes.
Strain bay leaf and peppercorns. Reserve liquid. Place vegetables in a 1-quart container. Pour liquid over vegetables and let sit for two days before using.