In a small bowl or jar with a lid, combine the red wine vinegar, Dijon mustard, oregano, garlic powder, salt, and black pepper. Whisk or shake until the ingredients are well combined.

Gradually add the olive oil in a thin stream while whisking continuously, or add it to the jar and shake vigorously until emulsified. Makes about ⅔ cup of dressing.

Taste and adjust seasoning if necessary. Use it with your favorite salads.