Preheat oven to 450F.
Lightly grease a rimmed baking sheet with cooking spray and set aside.
In a large mixing bowl combine trimmed brussels sprouts, olive oil, salt and pepper; mix until well combined.
Transfer brussels sprouts to previously prepared baking sheet; arrange in a single layer and bake for 15 minutes, stirring once or twice during cooking.
In the meantime, prepare the salmon.
Drizzle salmon with olive oil.
Evenly divide and press minced garlic on top of each fillet.
Season with oregano, salt and pepper.
Remove baking sheet from oven; move the brussels sprouts around, making 6 empty spots for the salmon fillets.
Place salmon in empty spots and bake for 10 to 12 minutes, or until salmon is cooked through.
Remove from oven; let stand 2 minutes and serve.