Thaw fish, if frozen. In a small mixing bowl, combine cilantro, oregano, lime juice, olive oil, garlic, and pepper sauce.
In a separate bowl, combine beans and avocado; stir in half of the cilantro mixture. Cover and refrigerate until serving.
Brush 2 tablespoons of the remaining cilantro mixture over fish. Place the catfish fillets on the lightly oiled rack of the grill directly over medium heat. Grill for 4 to 6 minutes or until fish flakes easily with a fork, turning once. Brush often with remaining cilantro mixture. Spoon most of bean and avocado relish equally onto 4 individual dinner plates. Arrange fish on relish; top with remaining relish.
Please note that some ingredients and brands may not be available in every store.