Start by placing your chicken breasts in a mixing bowl and pouring the marinade over them. Toss to coat, then cover and refrigerate for at least 30 minutes. If you have extra time, marinate overnight for even more flavor.
While your chicken marinates, heat olive oil in a saucepan over medium heat. Add the orzo and toast it lightly, stirring often. This step adds a nutty undertone to the orzo. Afterward, stir in the chili powder, tomato paste, and chicken broth. Bring everything to a boil, reduce the heat, and cover the pan. Simmer for about 15 minutes, or until the liquid is absorbed. Fluff the orzo with a fork once cooked.
Preheat your grill or grill pan to medium-high heat. Remove the marinated chicken from the fridge and grill it until fully cooked, with an internal temperature of 165°F. This usually takes about 6-7 minutes per side, depending on the thickness.
While the chicken is cooking, combine the diced Velveeta and undrained diced tomatoes in a microwave-safe bowl. Heat the mix on high in 30-second intervals, stirring after each burst, until the cheese is fully melted and the sauce is smooth.
To serve, spoon the orzo onto plates, place the grilled chicken breasts on top, and pour a generous ladle of queso over each piece. Make sure everything is nice and hot before serving!