Step 1

Heat a grill to medium-high. Season steak with salt and pepper. Brush corn and onion with olive oil; season with salt and pepper. Lightly brush grates with vegetable oil.

Step 2

Grill corn, turning occasionally, until lightly charred, 10 to 12 minutes. Grill onion until lightly charred and tender, 6 to 8 minutes a side. Transfer vegetables to a cutting board. When cool enough to handle, cut kernels from cobs and coarsely chop onion.

Step 3

Meanwhile, grill steak until a thermometer inserted into thickest part registers 125°F for medium-rare, about 3 minutes a side. Transfer to a plate; drizzle with 2 tablespoons vinaigrette. Let stand 10 minutes, then slice against the grain.

Step 4

In a large salad bowl or platter, layer romaine, bell pepper, tomatoes, corn, and onion. Season to taste; drizzle with half of remaining vinaigrette. Top with steak and feta. Serve with remaining dressing on the side.