In a bowl, whisk together the olive oil, lemon juice, minced garlic, oregano, cumin, paprika, salt, and pepper. This is your marinade base.
Add the chicken pieces to the bowl and toss to coat. Let the chicken marinate for 15 minutes while you prep the vegetables. If you have more time, you can marinate up to 2 hours in the fridge for deeper flavor.
Thread the marinated chicken onto skewers, alternating with pieces of bell pepper, red onion, and a few cherry tomatoes. Don’t crowd the pieces; give them a little space for even grilling.
Preheat the grill to medium-high heat. If using a charcoal grill, wait until the coals have a light ashy glow. If using a gas grill, you want steady, medium-high heat.
Grill the skewers for about 10 to 12 minutes, turning every 2 to 3 minutes to develop a nice char on all sides and to ensure the chicken cooks through. The internal temperature should reach 165°F (74°C).
If your vegetables need a bit more time, you can move the skewers to a cooler part of the grill or finish them on a sheet pan under the broiler for a couple of minutes to caramelize the edges.
Remove from heat and let rest for a couple of minutes before serving. This helps the juices redistribute and keeps the chicken juicy.
Serve with a light drizzle of lemon juice or a small dollop of yogurt or tzatziki if you like a creamy tang. A simple side of couscous, flatbread, or a crisp salad completes the plate.