Crockpot Cantonese Pork Dinner

2 pounds pork steaks cut into strips
2 tablespoons vegetable oil
1 onion, thinly sliced
1 (4.5 ounce) can mushrooms, drained
1 (8 ounce) can tomato sauce
3 tablespoons brown sugar
1 1/2 teaspoons distilled white vinegar
1 1/2 teaspoons salt
2 tablespoons Worcestershire sauce

In a heavy skillet, heat oil over medium high heat. Add pork strips and
brown. Drain off excess fat. Place meat, onion, mushrooms, tomato
sauce, brown sugar, vinegar, salt, and Worcestershire sauce in a slow
cooker. Cook on High for 4 hours, or on Low for 6 to 8 hours. Serve
over rice.