In a small bowl, whisk together olive oil, red wine vinegar, lemon juice, Dijon mustard, oregano, and salt and pepper to taste (I like 1/2 teaspoon salt and 1/4 teaspoon pepper).
Dijon mustard: Sometimes I use up to 1 tablespoon Dijon in this recipe because I love the flavor. Spicy brown mustard works too.
Oregano: Or substitute Italian seasoning or your favorite minced fresh herbs (such as basil, chives, and parsley).
Salt and pepper: I recommend tasting the dressing before you add any salt. Then, add ¼ teaspoon salt and taste it again. Once I figure out the salt, I generally add 50% of that amount of freshly ground black pepper (that's a ratio I learned in culinary school and I like it).
Yield: This recipe makes ¾ cup dressing, enough for 6 servings (2 tablespoons each). 1 recipe of dressing will dress 8-10 cups salad.
Storage: Store covered in the refrigerator and use within 4 days.
Make the dressing your own:Try adding a teaspoon of honey, a minced clove of garlic, or a pinch of red pepper flakes.