To the container of a blender or food processor, add the parsley, oregano, cilantro, onion, and garlic and pulse to mince. Add the red pepper flakes, olive oil, vinegar, and lemon juice and pulse 2-3 times to mix. Season with kosher salt and add more to taste. Or, finely mince all of the ingredients with a sharp knife, then whisk with the olive oil, vinegar, and lemon juice in a bowl or shake in a covered glass jar. Make ahead and store in the refrigerator 1-3 days or until ready to serve.

Heat the grill at medium-high heat (400-450°F) and brush the grill grates clean. Cut each eggplant crosswise into 1/2-inch thick slices. Lightly brush both sides of the eggplant slices with oil and season with kosher salt and freshly ground black pepper.

Grill the eggplant with the lid closed for 5-7 minutes each side, turning once, or until the slices become tender and are well grill-marked.

Remove from the grill and drizzle the warm eggplant with the chimichurri sauce to taste. Serve warm or at room temperature with more chimichurri sauce on the side. Leftover sauce can be refrigerated for up to 1 week.