In a small bowl, whisk together the balsamic vinegar, 1 tablespoon of olive oil, minced garlic, oregano, salt, and pepper to create a marinade.
Place the flank steak in a shallow dish and coat with half of the marinade mixture; let it sit for at least 15 minutes at room temperature.
Preheat an outdoor grill or indoor cast-iron grill pan to medium-high heat (approximately 400°F).
Grill the steak for 5 to 7 minutes per side or until the internal temperature reaches 135°F for medium-rare.
In a separate skillet or on a grill mat, sear the corn kernels for 3 to 5 minutes until lightly charred.
Remove the steak from the heat and allow it to rest on a cutting board for 10 minutes to redistribute juices.
Thinly slice the steak against the grain into 1/4-inch strips.
In a large mixing bowl, toss the mixed greens, cherry tomatoes, red onion, and charred corn with the remaining half of the marinade.
Divide the salad base into four portions and top each with equal amounts of sliced steak and gorgonzola crumbles.