Gather all your fresh ingredients: parsley, cilantro, garlic, onion, red chili peppers, and oregano. Wash parsley and cilantro thoroughly. Peel garlic and onion, and quarter the onion for easier chopping.

In a food processor, add parsley, cilantro, garlic, quartered onion, red chili peppers, and oregano. Pour in olive oil and lime juice or vinegar. Pulse until roughly chopped.

Taste the chimichurri and adjust salt and pepper as needed, then pulse again briefly. For a creamier texture, pulse longer without turning it into a paste.

Transfer the chimichurri to a mason jar or bowl. Serve it immediately over grilled steak, chicken, or roasted vegetables, or store in the fridge.