In a large skillet, heat oil over medium-high heat until shimmering. Add peppers and onions, season with oregano, salt, and pepper.
Cook 5-6 minutes until slightly softened but still tender-crisp. Remove from heat and set aside.
Arrange equal parts of rice and lettuce in 4 bowls. Top with fajita veggies, beans, salsa, guacamole, cheese, and sour cream. Season with salt and pepper, garnish with cilantro, and serve immediately.
Notes
Serve with sliced cooked chicken or ground beef, if desired.
Storage: Store leftovers in a sealed container in the refrigerator for up to 3 days.