To save time, make this refreshing salad the day before you plan to serve it.
Grate 1 1/2 tablespoons rind, and set aside. Peel and section oranges over a bowl to measure 3 cups; squeeze membranes to extract juice. Set sections aside, reserving 1/2 cup juice. Discard membranes. Combine rind, reserved juice, oil, salt, and pepper in a blender, and process until smooth.
Trim tough outer leaves from fennel; mince feathery fronds to measure 1/4 cup. Remove and discard stalks. Cut fennel bulb in half lengthwise; discard core. Cut each half crosswise into thin slices to measure 3 cups. Combine fennel, orange sections, and juice mixture, and toss gently. Sprinkle with fronds.