Rinse fresh parsley and cilantro under cold water to remove any dirt. Pat dry and remove thick stems.

In a food processor, combine parsley, cilantro, garlic, oregano, red pepper flakes, salt, and black pepper. Pulse until roughly chopped.

With the processor running, drizzle in olive oil, then add red wine vinegar and lemon juice. Blend until combined.

Taste and adjust seasoning with more vinegar or lemon juice, and red pepper flakes if desired.

Transfer chimichurri sauce to a bowl or jar. Serve immediately or refrigerate for up to a week.