Preheat grill to medium, about 400°F (200°C). Oil grate with a brush or oil-soaked paper towel.

Pat trout dry. Rub inside and out with salt, pepper, and olive oil. Place 1 tbsp butter, 2 lemon slices, and 2 dill sprigs inside each fish.

Grill trout skin-side down over direct heat for 4–5 minutes. Flip carefully and grill 3–4 more minutes, until flesh flakes and internal temp reaches 145°F (63°C).

Remove fish to a plate and let rest 2 minutes. Serve with extra lemon wedges.