Sweet-and-Sour Popcorn Chicken

1 medium green pepper, cut into 1-inch pieces
1 small onion, thinly sliced
1 tablespoon vegetable oil
1 can (20 ounces) unsweetened pineapple chunks
3 tablespoons white vinegar
2 tablespoons soy sauce
2 tablespoons ketchup
1/3 cup packed brown sugar
2 tablespoons cornstarch
1 package (12 ounces) frozen popcorn chicken

In a large skillet or wok, stir-fry green pepper and onion in oil for 3-4 minutes or until crisp-tender.

Drain pineapple, reserving the juice in a 2-cup measuring cup; set pineapple aside. Add enough water to the juice to measure 1-1/3 cups; stir in the vinegar, soy sauce and ketchup.

In a bowl, combine brown sugar and cornstarch. Stir in pineapple juice mixture until smooth. Gradually add to the skillet.

Bring to a boil; cook and stir for 2 minutes or until thickened. Add pineapple. Reduce heat; simmer, uncovered, for 4-5 minutes or until heated through.

Meanwhile, microwave chicken according to package directions. Stir into pineapple mixture. Serve immediately. Makes 4 servings.