In a large mixing bowl, combine the chopped spinach, artichoke hearts, cream cheese, Parmesan cheese, mozzarella cheese, minced garlic, lemon juice, dried oregano, salt, and pepper. Mix until well blended.
Place the salmon fillets on a parchment lined baking tray, skin side down. Using a sharp knife, make a pocket in each fillet by slicing it lengthwise but not all the way through.
Generously stuff each salmon fillet with the spinach-artichoke mixture. Press the edges gently to secure the filling.
Drizzle a little olive oil over the stuffed salmon and season the outside with salt and pepper.
Bake in the preheated oven for 20-25 minutes, or until the salmon is cooked through and flakes easily with a fork.
Optional: For a golden top, broil the salmon for the last 2-3 minutes.
Notes
Serve with sautéed vegetables and lemon wedges for garnish.