In a large bowl, stir together the yogurt, lemon juice, curry paste, 1/2 teaspoon salt and garlic powder. Add the chicken pieces and stir to coat. Cover and marinate in the fridge for at least 1 hour and up to 8 hours.
If using wooden skewers, soak in warm water for at least 30 minutes.
Preheat the grill to medium-high heat. Lightly brush the grill with canola oil.
Place the onion and red bell pepper pieces in a medium bowl. Toss with olive oil, ¼ teaspoon salt and pepper.
Thread the chicken (shake off and discard excess marinade), onion and red bell pepper pieces onto 6 skewers.
Grill until the chicken is cooked through, about 12 minutes, turning halfway through cooking. Serve.