Slow Cooker Enchilada Quinoa Bake

• 1 Tbsp canola oil
• 1 1/4 cups chopped yellow onion (1 medium)
• 1 1/4 cups chopped red bell pepper (1 medium)
• 3 cloves garlic, minced
• 1 1/2 cups dry quinoa
• 2 1/4 cups vegetable broth
• 1 (14.5 oz) can tomatoes with green chilies, undrained
• 1 (8 oz) can tomato sauce
• 2 Tbsp chili powder
• 1 1/2 tsp ground cumin
• Salt and freshly ground black pepper, to taste
• 1 (14.5 oz) can black beans, drained and rinsed
• 1 (14.5 oz) can pinto beans, drained and rinsed
• 1 1/2 cups frozen corn
• 1 1/2 cups cheddar or monterey jack, or Mexican blend cheese

For serving

• Diced avocados , diced Roma tomatoes, chopped cilantro, lime wedges, chopped green onions (optional)