Combine balsamic vinegar, olive oil, garlic, salt, and fresh groud pepper in a large plastic bag. Add pork tenderloin to marinade and refrigerate 10 minutes to 10 hours (delicious no matter how long it marinates).
Remove tenderloin from marinade and place on heated grill. Grill for 20 minutes turning after 10 minutes.
Remove from grill (internal temperature should be 160 degrees) and let sit for 5-10 min. Slice and serve.
Recipe by One Green Fork at https://www.onegreenfork.com/grilled-balsamic-pork-tenderloin/