Drain artichokes, reserving marinade (to yield about 1/3 cup). Finely chop artichokes.
Combine in a medium bowl the artichokes, zucchini, tomato, and green onion. Combine in small bowl the reserved marinade, basil, garlic and lemon juice and whisk together. Pour over artichoke mixture; toss gently to coat. Cover and chill for 2 to 6 hours, stirring occasionally.
To serve, remove cores from Belgian endives. Separate endives into leaves. Drain artichoke mixture. Spoon about 2 teaspoons of the artichoke mixture on each leaf.