Slice the cod fillets into smaller pieces or keep them whole. Next, slice the onion and bell peppers into bite-sized pieces.
Place all the vegetables in one layer on the baking sheet. Assemble the cod evenly throughout the pan. Season with garlic parsley salt and add chunks of butter on top of the cod.
Bake the cod at 400°F for about 15 minutes. It'll be ready once its internal temperature reaches 145°F. Enjoy!