In a large nonstick skillet, sauté chicken tenderloins with salt and pepper to taste. Add mushrooms, red bell peppers, and yellow bell peppers, cooking until vegetables are tender.

Cook spaghetti according to package directions. Drain and set aside.

In a large saucepan, melt butter and blend in flour. Gradually stir in chicken broth and half-and-half. Cook over medium-low heat while stirring constantly until the sauce begins to thicken.

Add garlic salt, ground black pepper to taste, and blend in Swiss and Parmesan cheeses. Continue heating and stirring until cheeses melt.