Combine garlic, oil and red wine vinegar in a shallow dish. Add kangaroo fillets and toss to coat. Cover and refrigerate for 2 hours.
To prepare potato salad, cook potatoes in a large saucepan of boiling, salted water for 10 minutes, until just tender. Drain. When cool enough to handle, peel and slice thickly. Add hot potatoes to combined oil, lemon juice, capers and garlic. Gently toss to coat. Cook bacon in a non-stick frying pan on high heat for 3 minutes, until crisp. Add to potatoes with chives and toss.
Cook kangaroo on a chargrill or barbeque, on high heat sear for 3 minutes each side, turn heat down and continue to cook for an extra 3-5 minutes for medium rare or to liking. Remove from heat, cover with foil and rest for 5 minutes. Slice and serve with warm potato salad and baby cos leaves.