1 can (6 1/2 oz.) crab, drained
1 pkg. (3 oz.) cream cheese, softened
1 tbsp. mayonnaise
2 tsp. diced pimiento
1 tsp. prepared mustard
1/2 tsp. lemon juice
1/2 tsp. minced onion
48 fresh mushroom caps

Combine all ingredients, except mushrooms, in small mixing bowl; blend well. Fill each mushroom cap with about 1 teaspoon filling. Arrange 10 to 12 mushrooms, stuffing-side up, in a circle on microproof plate. Cook on HI 1 1/2 to 2 minutes, or until heated through. Repeat with remaining mushrooms.