Cook the farro in a large pot of salted water until tender, about 20 minutes. Drain and rinse under cold water, then transfer to a large bowl.
In a small bowl, whisk together 2 tablespoons olive oil, the lemon juice, lemon zest, minced garlic, parsley, mint, salt, and black pepper to make the dressing.
Pour half the dressing over the cooled farro and toss to coat. Set the remaining dressing aside.
Heat a grill pan over medium-high heat and brush with the remaining tablespoon of olive oil. Grill the zucchini slices and red bell pepper quarters until lightly charred, about 3 to 4 minutes per side. Grill the halloumi slices for 1 to 2 minutes per side until golden.
Add the cherry tomatoes to the farro. Slice the grilled vegetables into bite-size pieces and arrange them over the farro along with the grilled halloumi. Drizzle with the remaining dressing just before serving.