Add the portobello caps, peppers, and zucchini to a large bag or bowl. In a separate small bowl, whisk together the olive oil, balsamic vinegar, garlic, basil, blackberry jam, and a pinch of salt and pepper. Pour over the veggies and toss to combine. Let marinate 15 minutes at room temperature, or up to 12 hours in the fridge.
Preheat grill or grill pan to medium heat and lightly spray with oil. Grill veggies 3-4 minutes per side until charred and tender - grill the mushrooms whole. The mushrooms may take a bit longer. If you are using a small grill pan, factor in extra cook time since you will likely be working in smaller batches. Set the cooked veggies on a plate and cover to keep warm.
Heat broiler to HIGH. Slice the large ciabatta loaf in half lengthwise and brush both cut sides with oil. Broil about 2-3 minutes. Watch very closely to prevent burning.
To make the tapenade, combine all ingredients to a food processor and pulse until chunky but well combined.
Assemble the sandwich! Spread the tapenade over the cut side of the bottom bread slice. Stack the zucchini, then the bell peppers. Slice the mushroom caps into strips and pile atop the peppers. Dot brie over the mushrooms and finish with a big pile or arugula. Slice into 4-8 sandwiches (depending on how big you want them). Enjoy!