1. Peel and chop 1 peach. Cut remaining 4 peaches into 28 (1/4-inch-thick) rounds, cutting through stem and bottom ends. (Cut peaches inward from sides, cutting each side just until you reach the pit. Discard pits.)
2. Process chopped peach, green onions, next 7 ingredients, and, if desired, tequila in a food processor 10 to 15 seconds or until smooth. Add oil, and pulse 3 to 4 times or until thoroughly combined.
3. Coat cold cooking grate of grill with cooking spray, and place on grill. Preheat grill to 350° to 400° (medium-high). Brush both sides of peach rounds with 1/3 cup peach dressing.
4. Grill peach rounds, covered with grill lid, over 350° to 400° (medium-high) heat 3 to 5 minutes on each side or until grill marks appear.
5. Arrange watercress evenly on 4 plates. Alternately layer 4 grilled peach rounds and 4 cheese slices over watercress on each plate. Top each with 3 more peach rounds. Drizzle with remaining peach dressing. Garnish, if desired.
Grilled Peach-and-Feta Salad: Preheat oven to 350°. Arrange 1/4 cup pecans, chopped, in a single layer in a shallow pan. Bake 8 to 10 minutes or until toasted and fragrant, stirring after 5 minutes. Reduce peaches from 5 to 4, and reduce salt to 1/2 tsp. Substitute 8 cups loosely packed Bibb lettuce leaves (about 6 oz.; 1 to 2 heads of lettuce) for watercress and 1/4 cup crumbled feta cheese for mozzarella cheese. Peel and chop 1 peach. Cut each of remaining 3 peaches into 8 wedges. Proceed with recipe as directed in Steps 2 through 4, decreasing grilling time for peach wedges to 2 to 3 minutes on each side or until grill marks appear. Divide Bibb lettuce and 4 cooked bacon slices, halved crosswise, among 4 plates or shallow bowls. Top with grilled peach wedges. Sprinkle with feta cheese and pecans. Serve with dressing. Makes 4 servings; Prep: 25 min., Bake: 10 min., Grill: 6 min.
Note: You can also use a grill pan to get those beautiful grill marks on the peaches.