Arrange potato wedges in an even layer on a lightly greased broiler pan; coat wedges with vegetable cooking oil spray. Bake at 475 degrees for 20 to 25 minutes or until tender and golden.
While potatoes are roasting, cook the bacon. Drain, crumble and set aside.
Whisk together lemon juice and next 5 ingredients; whisk in oil in a slow, steady stream. Gently toss potatoes, onion, and 1/2 cup lemon mixture.
Wash spinach thoroughly; pat dry with paper towels or spin dry. Arrange spinach evenly on a platter or in 6 individual bowls. Drizzle with remaining lemon juice mixture. Top with potato mixture and sprinkle with the bacon.