On 6 large pieces of parchment paper, divide asparagus spears and green onions evenly.
Season fish with salt and pepper and place on top of vegetables.
Curve up the edges of parchment a little so the liquid doesn’t run off, then sprinkle oil and wine over top. Top with lemon slices.
Wrap each packet with the seam on top, rolling seam over itself once or twice to seal tightly and leaving a little room inside parchment for steam to circulate.
Place packets in cast iron skillet or fire-safe pot on grill rack over a medium flame for 10 to 15 minutes, rotating packages occasionally for even cooking.