Cut the venison loin into 1-inch cubes and place them in a glass mixing bowl.
Whisk together the extra virgin olive oil, minced fresh rosemary, minced garlic, balsamic vinegar, sea salt, and black pepper in a small jar.
Pour the marinade over the venison cubes, tossing thoroughly to coat, and allow to marinate for 20 to 30 minutes at room temperature.
While the meat marinates, chop the red bell pepper, red onion, and zucchini into 1-inch pieces suitable for skewering.
Thread the marinated venison and the chopped vegetables onto skewers, alternating between the meat and the various vegetables.
Preheat your grill to medium-high heat and lightly brush the grates with a touch of oil to prevent sticking.
Place the skewers on the grill and cook for 3-4 minutes per side, turning occasionally until the venison is medium-rare and the vegetables are tender-crisp with light char marks.
Transfer the kebabs to a clean plate and let the meat rest for 5 minutes before serving to lock in the juices.