Wash and dry all produce. Preheat broiler or grill to high. Place skewers in a wide bowl, cover with water, and let soak. Core and finely dice tomato. Cut corn kernels from cob. Core, seed, and cut bell pepper into 1-inch squares. Slice zucchini into 1/4-inch-thick rounds. Trim, then halve mushrooms. Mince garlic. Chop parsley.

Bring 1 cup water and a pinch of salt to a boil in a small pot. In a small bowl, combine garlic, 1/2 TBSP white wine vinegar, 1 tsp mustard, and 1 TBSP olive oil. Season with salt and pepper.

Once water is boiling, add couscous to pot. Cover and remove from heat. Let stand until rest of meal is ready.

Remove skewers from water. Thread mushrooms, zucchini, and bell pepper onto skewers, alternating between each. Brush with marinade. Season with salt and pepper. Place on a baking sheet. Broil until lightly charred and tender, 6-8 minutes per side. TIP: If grilling, place skewers on grate directly over flame and cook 6-8 minutes per side.

Heat 1 TBSP olive oil and 1 TBSP butter in a large pan over medium heat. Add tomato and corn. Cook until tomato softens, 4-5 minutes. Stir in 1 TBSP white wine vinegar and 1 tsp mustard. Remove pan from heat and let stand a few minutes to cool, then stir in feta cheese. Season with salt and pepper.

Fluff couscous with a fork, then stir in parsley, 1 TBSP butter, and a drizzle of olive oil. Season with salt and pepper. Divide couscous between plates, then top with relish and skewers.