Heat a grill pan over medium-high. Coat pan with cooking spray. Rub oil over pork. Add pork to pan; loosely tent pork with foil. Grill 10 minutes, turning occasionally. You can also slice some fresh peaches and throw them on the grill while the pork is cooking, turning often.
While pork cooks, combine peach preserves, soy sauce, vinegar, and garlic in a microwave-safe bowl. Microwave at HIGH 30 seconds or until preserves melt. Grill pork 6 minutes more, or until thermometer registers 145°F, turning and brushing frequently with peach glaze. Remove pork from pan; let stand 3 minutes. Cut pork crosswise into slices. Sprinkle evenly with salt and pepper.