Heat oven to 300°F. In large bowl, mix cereals, pretzels, crackers and soy nuts.
In small bowl, mix oil, vinegar, garlic salt and Italian seasoning. Pour over cereal mixture, stirring to coat. Spread in ungreased 15x10x1-inch pan.
Bake about 30 minutes, stirring twice, until toasted. Sprinkle with cheese; toss to coat. Cool completely, about 45 minutes. (Cereal will crisp as it cools.) Store in airtight container.