Combine oysters and buttermilk in a large shallow dish or zip-top plastic freezer bag. Cover or seal and chill at least 2 hours. Drain oysters well.
Combine flour and the next 9 ingredients. Dredge oysters in flour mixture, shaking off excess.
Pour oil to a depth of 1 inch in a Dutch oven; heat to 370°.
Fry oysters, in batches, 3 minutes or until golden. Drain on paper towels. Serve immediately.
Fried Buffalo Oysters: Prepare Southwest Fried Oysters as directed, omitting the chili powder. Stir together 1/2 cup melted butter, 1/2 cup hot sauce, and 2 tablespoons fresh lemon juice. Pour butter mixture evenly over hot fried oysters. Serve oysters with Ranch dressing and celery sticks on the side.
Fried Buffalo Oyster Po'Boys: Prepare Fried Buffalo Oysters as directed. Split 4 French bread rolls. Spread 1 tablespoon mayonnaise evenly on cut sides of rolls. Place 1/4 cup shredded iceberg lettuce and one-fourth of Buffalo Oysters on bottom halves of rolls; cover with roll tops.