PREHEAT barbecue to medium-high. Slice baguette in half lengthwise and set aside. In a small bowl, whisk together 3 tbsp (45 mL) oil and garlic paste. Brush evenly onto cut sides of baguette. Grill 1 to 2 min. per side, then place on top rack until toasted, 6 to 8 min. Remove from heat.
FIRMLY rub halved tomatoes onto grilled baguette so tomato becomes crushed and pulpy. Top with feta and arugula, season with pepper, then drizzle with remaining oil. Slice each baguette half into 8 pieces and serve.