Heat grill or grill pan until hot. Bring 3/4 cup water to a boil in a medium saucepan. Add couscous and pinch of salt; stir. Cover, remove from heat, and let stand 5 minutes. Fluff couscous with a fork.
Combine lemon juice and zest, couscous, thyme, and mayonnaise in a bowl. Season with salt and pepper. Set aside.
Snap off and discard tough ends of asparagus. In a large bowl, combine asparagus, onion, and oil; season with salt and pepper.
Grill asparagus and onions until spears are slightly charred and rounds are soft and browned, about 10 minutes.
Spread one-fourth of couscous over each piece of flatbread. Place 4 asparagus spears, tips extending, over couscous. Place one-fourth of onions on asparagus; top with one-fourth of the lettuce. Roll each sandwich tightly; seal with a wooden skewer. Serve.
OH DEAR! A PITA IS NOT MADE TO ROLL UP.... GO TO THE TOP OF PAGE TO THE "ALSO TRY" AND LOOK FOR THE CHICKEN SALAD PITAS, THE PICTURE SHOWS US HOW TO FILL A SANDWICH. GOOD LUCK. GRANNY S.
I used pita bread for this and it wasn't really the optimal choice...the sandwich didn't really roll up well and it was difficult to eat. It was quite tasty all the same and the couscous was complimented in particular. Might try tortillas next time to see how that works out for us. I'll def fix this again.