Thaw frozen fish.
Cook onion in 2 tablespoons butter.
In a large bowl combine cooked onion, bread cubes, cucumber, green pepper, parsley, lemon peel, thyme, sage, 1/4 teaspoon salt,and dashpepper.
Sprinkle cavity offish with salt and pepper.
Place in well-greased shallow baking pan.
Stuff fish with bread mixture.
Brush with melted butter; drizzle with lemon juice.
Cover pan with foil.
Bake at 350° till fish flakes easily when tested with a fork, 45 to 60 minutes.
Transfer fish to serving platter.