Cook fennel seeds, black peppercorns, and dried crushed red pepper in a small saucepan over medium heat, stirring constantly, 1 to 2 minutes or until fragrant and lightly toasted. Add 1/2 cup liquid from jarred Spanish olives, bay leaves, orange peel strips, and rosemary sprig, and bring to a boil. Remove from heat, and add vermouth. Combine olives and cocktail onions in a medium bowl; spoon into 4 (8-oz.) jars. Place 1 bay leaf and 1 orange peel strip from vermouth mixture in each jar, and fill with vermouth mixture. Cover with lids. Chill 4 hours before serving. Store in refrigerator up to 3 weeks.
TO USE THE OLIVES: Serve as a cocktail garnish or bar snack.
PACKAGE THEM IN: Weck Tall 9.8-oz. Glass Jar ($3.50; westelm.com).