Preheat oven to 450˚F.
Lightly grease a rimmed baking sheet with cooking spray and set aside.
In a large mixing bowl, combine trimmed brussels sprouts, olive oil, garlic, salt, and pepper; mix until well combined.
Transfer brussels sprouts to the prepared baking sheet; arrange them in a single layer and bake for 14 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 salmon with oregano, salt, and pepper.
Remove the baking sheet from the oven; move the brussels sprouts around to make room for the salmon fillets.
Place salmon on the baking sheet and bake for 10 to 12 minutes or until salmon is cooked through.
Remove from oven; let stand 2 minutes and serve.