Cook the grain base. Rinse brown rice or quinoa. Cook according to package directions. Fluff with a fork and set aside.
For extra flavor, add a pinch of salt and a splash of lime juice while it rests.
Preheat and prep. Heat the oven to 425°F (220°C). Line two sheet pans with parchment for easy cleanup.
Season the chicken. Pat the chicken dry. In a bowl, mix smoked paprika, garlic powder, onion powder, chili powder, salt, and pepper with 1 tablespoon olive oil.
Toss the chicken to coat evenly.
Add the BBQ sauce. Brush or toss chicken with 1/2 cup of the BBQ sauce, reserving the remaining 1/2 cup for finishing after baking.
Chop the vegetables. Slice bell peppers and red onion into strips. Cut zucchini into half-moons. Toss peppers, onion, and zucchini with 2 tablespoons olive oil, a pinch of salt, and pepper.
Arrange on sheet pans. Place chicken on one pan, spaced out.
Spread vegetables on the other pan in a single layer. If using frozen corn, scatter it over the vegetable pan. If using canned corn and black beans, set aside to add after roasting.
Roast. Bake the chicken for 16–20 minutes, until the internal temperature reaches 165°F (74°C).
Roast vegetables for 15–18 minutes, tossing once, until tender and slightly charred at the edges.
Finish the chicken. Brush the hot chicken with the remaining 1/2 cup BBQ sauce. Let rest for 5 minutes, then slice or cube.
Warm the beans and corn (if not roasted). If you didn’t roast the corn, quickly warm the corn and black beans together in a skillet with a pinch of salt and a squeeze of lime. This helps them taste fresh and meld with the BBQ flavor.
Assemble the bowls. Divide the cooked grain among containers.
Top with sliced BBQ chicken, roasted vegetables, black beans, and corn. Add sliced avocado, chopped cilantro, green onions, and lime wedges if you’re eating soon. If storing for later, add avocado and lime the day you eat.
Optional sauce. Stir 1/2 cup Greek yogurt with 1 tablespoon BBQ sauce and a splash of lime juice for a quick, creamy drizzle.
Keep it in a separate container and add just before serving.