Heat oil in a large skillet over medium-high heat. Add couscous, and cook, stirring, for 1 minute. Transfer to a bowl, and return skillet to heat.
Cook chicken, smooth side down, until browned, 3 to 5 minutes. Flip, and cook for 2 minutes more. Transfer to a plate, reserving drippings in skillet.
Reduce heat to medium, add onion, and cook, stirring frequently, for 3 minutes. Stir in tomatoes, garlic, lemon peel, and saffron, and cook, stirring frequently, until tomatoes begin to break down, 2 to 3 minutes.
Return chicken to skillet. Add wine, and cook for 4 minutes. Add stock, salt, and couscous, and stir. Reduce heat to medium-low, cover, and cook, stirring occasionally, until couscous is tender and chicken is cooked through, 12 to 14 minutes. Stir in peas, and cook until heated through, about 1 minute. Serve immediately with lemon.