To make the chimichurri, combine all ingredients in a bowl and season to taste with salt and pepper. Set aside.
Combine marinade ingredients (white vinegar through to cumin) in a large zip-top bag or ceramic dish. Add beef, stir to coat, and marinate for 30 mins.
Drain beef, discarding marinade. Thread meat onto skewers, alternating a piece of capsicum between each piece of beef, and season with salt and pepper. Preheat BBQ or a heavy-based pan to high. Cook skewers, turning to sear all sides, for 4–5 mins.
Cut corn kernels off the cob. Combine corn, roasted sweet potato, and rocket on a large platter. Drizzle over 1–2 tbsp chimichurri sauce and toss to coat.
Serve beef skewers with salad and chimichurri.
To roast sweet potatoes, toss with 1 tbsp olive oil, season with salt and pepper and bake for 25 mins at 180°C. Alternatively, cook on the BBQ, over medium-low heat, until tender.