1. Preheat grill to medium-high. Slice each potato in half lengthwise, then slice each half into wedges about 1/2-inch thick. Place in a medium bowl and combine with oil, salt, and rosemary. Set aside.
2. Rinse tilapia under cold water and pat dry with a paper towel. Season with pepper. Combine bread crumbs, parsley, lemon zest, and cayenne in large bowl. Whisk egg whites and beer in a separate medium bowl. Add fish to the egg mixture and turn to coat, then turn fish in bread crumb mixture to coat both sides. Set aside.
3. Place sweet potato wedges on a grill rack or basket and grill for approximately 5 minutes per side or until marked. Transfer to the top rack of the grill to keep them heated while the fish cooks.
4. Place tilapia either directly on the grill or on a sheet of heavy-duty foil on the grill and cook for 4 to 5 minutes per side, or until opaque throughout. Serve immediately with chips and a wedge of lemon.
Source: fresh magazine May, June 2010