Cut meat into 1-inch cubes, about 32 pieces; wash hands.
Combine salsa, Worcestershire sauce, and soy sauce. Reserve 1/4 cup marinade; place remaining marinade and steak in bag. Seal bag and knead to coat; let stand 15 minutes to marinade (or overnight).
Thread onions and meat alternately on skewers. Place skewers on grill; grill 4–5 minutes, turning often, or until meat is 145°F (for medium rare). Baste skewers with reserved 1/4 cup marinade during last 2 minutes of grill time. Serve.
Stuffed Mini-Sweet Peppers:
Remove stem end of peppers; slice peppers in half lengthwise and remove seeds and white membrane.
Cut bacon slices in half.
Combine cream cheese and shredded cheese. Arrange peppers on work surface with cut side up; divide cheese mixture and fill each pepper half.
Wrap one-half slice bacon around each pepper and secure ends with toothpicks.
Place peppers on grill over indirect heat; grill 2 minutes or until cheese is melted and bacon is crispy. Remove toothpicks and serve.