Cut beef into 1/4-inch-thick slices about 1-1/2 inches long and 1/2 inch wide. Mix with spice mixture; cover and chill at least 1 hour or up to 4 hours. Stir occasionally. Using thin bamboo skewers (about 8 in. long), thread 3 or 4 slices marinated meat on each, weaving skewer in and out of each slice. (If making ahead, cover and chill up to a day.) Place skewers on a grill 4 to 6 inches above a solid bed of medium-hot coals (you can hold your hand at grill level only 3 to 4 seconds). Using lemon grass with slivered base or a brush, baste meat with oil. Cook meat, turning often, until evenly brown on both sides, about 4 minutes total. (Be careful not to burn the skewers.) Put on a large platter, along with onion and cucumber. Makes about 40 skewers, about 8 servings. Per serving: 249 cal. (47 percent from fat); 26 g protein; 13 g fat (2.6 g sat.); 8.6 g carbo.; 71 mg sodium; 70 mg chol. Satay Spice mixture: Mix 2 cloves garlic. minced or pressed; 1 large (about 1/2-lb.) onion. finely chopped; 2 tablespoons ground cumin; 2 tablespoons ground coriander; 1 tablespoon sugar; and 1 teaspoon ground turmeric.