In a small bowl, whisk together butter, parsley, chives, salt, and pepper, stirring until smooth.
Cut 4 (18x15-inch) pieces of foil. On each piece of foil, arrange squash and zucchini, overlapping slices. Place 1 catfish fillet on top of squash mixture; top with onion. Arrange tomatoes around fillet. Top with about 2 tablespoons butter mixture. Fold foil over fillet and vegetables and crimp edges to seal.
Grill foil packets until vegetables are tender and fish flakes easily, 15 to 20 minutes.
Serve with grilled bread. Garnish with parsley and chives, if desired.
Notes
RECIPE FOR SUCCESS To make this easy summer meal without a grill, preheat the oven to 400°. Place the foil packets on a rimmed baking sheet and bake until the vegetables are tender and fish flakes easily, 20 to 25 minutes.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/grilled-catfish-market-vegetables/