Cut four 15- x 12-inch pieces parchment paper or aluminum foil, fold in half lengthwise, creasing firmly.
Trim each into a large heart shape.
Place parchment hearts on baking sheets.
Lightly brush one side of each heart with 1 to 2 tablespoons vegetable oil, leaving edges ungreased.
Set aside.
Combine tomatoes, green onions, 2 tablespoons vegetable oil, lemon juice, and oregano, set aside.
Arrange snow peas attractively in a fan design on one greased half of each parchment heart, near the crease.
Sprinkle fillets with salt and pepper; arrange fillets over snow peas.
Spoon tomato mixture over fillets.
Fold over remaining halves of hearts.
Starting with rounded edge of each heart, pleat and crimp edges together to seal.
Twist end tightly to seal.
Bake at 450° for 10 to 12 minutes or until bags are puffed and lightly browned and fish flakes easily when tested with a fork.