In a large bowl stir together the yogurt, beer, red pepper, paprika, tomato paste, salt, pepper, and garlic. Add the chicken cubes, stir until fully submerged and coated. Cover and refrigerate for at least 2 hours and up to 24.
Preheat grill to medium high.
Remove chicken from marinate and thread onto metal skewers (or presoaked wood skewers), discard marinade.
Brush the grill with oil to prevent sticking.
Grill the chicken skewers on each side until cooked through, about 5 minutes per side.
Sprinkle with chopped parsley before serving, if desired.