Halloumi—a firm, salty cheese that doesn’t melt on the grill—is the star of this fun take on classic Greek salad.
Prepare the grill for medium-high heat. On a rimmed baking sheet, brush the bell pepper, tomatoes, radicchio, onion, and halloumi with 3 tbsp. oil; season with salt and pepper. Thread the tomatoes onto skewers. Grill the vegetables, turning occasionally, until tender and charred in spots, 3 to 4 minutes for the tomatoes, radicchio, and onion and 8 to 10 minutes for the bell pepper. Transfer the vegetables to a cutting board.
Grill the halloumi until grill marks form, 3 to 4 minutes per side. Transfer to the cutting board; let cool. Roughly chop the vegetables and halloumi. Transfer to a large bowl.
Add the beans, basil, olives, lemon juice, and the remaining 1 tbsp. oil. Toss until coated; season.