This is a great alternative to steaming your asparagus. If you don't have a grill, you can roast them in the oven at 400 degrees for 10-15 minutes, turning once. You could also just drizzle them with olive oil, salt and pepper and skip the marinade.
adapted from Cooking Light on MyRecipes.com
1-2 pounds fresh asparagus
2 Tbsp. balsamic vinegar
1 Tbsp. fresh lemon juice
1 Tbsp. olive oil
1 Tbsp. low-sodium soy sauce
1 clove garlic, pressed or minced
1/8 tsp. black pepper
Snap off ends of asparagus. Combine all ingredients except cooking spray in a gallon-size Ziploc bag. Marinate for 30 minutes.
Lightly coat grill grate with cooking spray. Preheat grill on high heat. Grill asparagus 2-3 minutes or until desired tenderness; discard marinade.