Transfer to a plate; keep warm. Reduce heat to medium- high.
Add onion and garlic to pan; sauté 3 minutes, stirring frequently. Add half of spinach; cook 1 minute, stirring frequently. Add remaining half of spinach; cook 2 minutes or just until wilted, stirring frequently. Remove from heat; stir in remaining 1/8 teaspoon salt and remaining 1/8 teaspoon pepper. Divide spinach mixture among 4 plates; top each serving evenly with crumbled bacon and 3 scallops. Serve immediately with lemon wedges, if desired.