Place steak in a baking dish. Combine olive oil, vinegar, garlic, cumin, salt, and pepper and pour over the steak, flipping the steak over a few times to coat. Cover with plastic wrap. Let sit at room temperature for 30 minutes, flipping the steak once or twice.

Prepare the grill for medium-high heat.

Oil the grill grates, remove the steak from the marinade, discarding the marinade, and grill over direct heat for 3–5 minutes per side, depending on thickness and desired doneness. For medium-rare, the internal temperature should be between 125–130°F.

Remove from grill and let sit for 5–10 minutes. Slice thinly across the grain and top with some of the chimichurri sauce and garnish with chopped parsley. Serve the rest of the chimichurri on the side.