In a large saucepan, cook fennel in a small amount of boiling water, covered, for 3 minutes. Add frozen vegetables and celery. Return to boiling; reduce heat. Cover and simmer about 5 minutes or until the vegetables are tender. Drain.
Meanwhile, in a small skillet cook sesame seed in hot olive oil for 1 to 2 minutes or until light brown. Remove from heat. Cool slightly. Carefully add lemon juice, salt, and pepper.
Pour sesame mixture over drained vegetable mixture. Stir gently until coated. Makes 6 side-dish servings.