Make the chimichurri
Add the parsley, cilantro, oregano, shallot, garlic, and jalapeño to a food processor.
Pulse until the herbs and aromatics are finely chopped, but not completely smooth.
Add the liquids
Pour in the lemon juice, red wine vinegar, olive oil, salt, and black pepper.
Pulse a few more times until the sauce is combined and spoonable. It should look rustic and herby, not creamy or fully blended.
Season the chicken
Place the chicken thighs in a shallow dish or large bowl.
Pat them dry, then season both sides with salt and pepper.
Marinate
Spoon about 1/4 cup of the chimichurri over the chicken.
Turn the chicken to coat it well. Cover and refrigerate for at least 20 minutes, or up to 24 hours for deeper flavor.
Preheat the grill
Heat your grill to medium-high.
Let the chicken sit at room temperature for about 10 to 15 minutes while the grill heats. This helps it cook more evenly.
Grill the chicken
Place the chicken thighs on the hot grill.
Cook for about 5 to 6 minutes per side, or until the chicken is nicely charred and cooked through.
Check for doneness
The chicken is ready when the thickest part reaches 165°F.
Let it rest for a few minutes so the juices settle.
Serve with extra sauce
Spoon fresh chimichurri over the grilled chicken just before serving.
Serve warm with your favorite summer sides.