Arrange tilapia on a sheet pan, drizzle with olive oil and juice of 1 lime, season with salt and pepper, and bake at 400°F for 12 minutes.
While fish cooks, heat a skillet over medium-high and sauté thawed corn with drained black beans until heated through, about 5 minutes.
Toss the bean mixture with chopped cilantro and juice from the second lime.
Plate fish over beans and top with sliced avocado.