Toss shrimp with chili powder, cumin, and salt. Heat a large nonstick skillet over medium heat. Add oil, swirling to coat. Add shrimp to pan, and cook 3 to 5 minutes or just until shrimp turn opaque, turning once.
Place 1 cup lettuce in each of four bowls; add ⅓ cup cooked quinoa to each bowl. Divide beans and shrimp evenly among bowls. Top each serving with 2 tablespoons salsa and 2 tablespoons guacamole. Serve with cilantro and lime wedges, if desired.