Arrange lemon slices in a small roasting pan and drizzle with olive oil. Broil 8 from the heat until lightly browned. Mix together melted butter and lemon juice.
Scatter thyme sprigs on top of browned lemons; top with fish fillets. Drizzle with butter/lemon juice mixture. Broil fish 4 from the heat for 10 to 12 minutes, or just until fish flakes easily when tested with a fork.